US 4409758

I'll verify this patent against live sources and check for any litigation activity.

Let me check for any litigation or Federal Circuit activity involving this patent or its assignee.

US Patent 4,409,758 — Verification Report

⚠️ Scope note on the number

I interpreted "4409758" literally as US 4,409,758 (US4409758A). Note that search results also surface JP 4409758 B2 (Toyobo Co., Ltd.; abrasive-sheet manufacturing method; registered 2009). That is an unrelated Japanese document and is not the patent you asked about. No results for any other US patent with a similar number were substituted.

Bibliographic data (confirmed against the Google Patents full text and cross-citations)

Abstract (as issued)

"An improved perimeter strip for a magnetically attached auxiliary window system which includes gasket means (1) on the interior surfaces of a glazing holding channel of the strip and (2) adjacent the magnetic attachment means, whereby a flexibly tensional relationship between the strip and the magnetically attractable means associated therewith is provided."

Independent claims

There is exactly one independent claim — claim 1. Claims 2–8 all depend (directly or indirectly) on claim 1 (claims 2–4 and 8 via dependency chains, claims 6–7 directly on claim 1). No method claims, no separate independent apparatus claim.

Claim 1 (plain language): It is an improvement claim written in Jepson-style format ("In an auxiliary window system … the improved perimeter strip which includes …"). The preamble environment has three parts: (1) a perimeter strip applied to the edge of a glazing pane, with the pane edge received in a longitudinal channel whose cross-section is formed by upper and lower segments of an integral member; (2) a magnetically attractable means running alongside and parallel to that channel-forming segment, co-extending along its outer surface; and (3) that attractable means being for attachment to a corresponding magnetic means placed around the prime window perimeter.

The improvement consists of two things:

1. Inwardly facing, longitudinally extending resilient gaskets on the inner surfaces of the pane-receiving channel (i.e., the co-extruded "feathers" that grip the glazing).
2. Resilient gasket feather means on the outer surface of the channel-forming segment, on the side facing the magnetically attractable means. These feathers must (a) run longitudinally along that outer surface, (b) be in sealing relationship with the attractable means, and (c) create a flexibly tensioned relationship between the channel segment and the attractable means — this is the "float" feature that lets the steel band pivot/conform to the prime-window magnet.

Dependent claims (substance):

• 2 — the attractable means is a longitudinal metal band, held in a slot defined by rigid legs extending perpendicularly from the lower channel segment.
• 3 — further gasket means extend outward from those legs so they overlap the prime-window magnet when installed (the anti-slide/anti-drop lip).
• 4 — the strip is a dual-durometer vinyl extrusion.
• 5 — rigid phase is polypropylene; co-extruded flexible phase is polyurethane.
• 6 — the gasket between channel member and attractable means is approximately centrally located across the width, producing a "floating pivot" relationship.
• 7 — dual-durometer plastic extrusion, rigid body with compatible co-extruded flexible plastic gaskets.
• 8 — the gaskets are a plurality of co-extruded feathers.

Prior art of record

Cited by the examiner (15 references), including: US 1,946,169 (Mackenzie); US 2,219,699 (Pittsburgh Plate Glass); US 2,595,833 (Flaherty); US 3,360,893 (Wattelez); US 3,363,390 (Crane Plastics — extruded panel-framing strip with rigid body and resilient gripping flanges); US 3,679,505 (3M); US 3,805,872; US 3,939,620, US 4,184,297, US 4,248,018 (all Plaskolite — the assignee's own earlier panel-holding strips); US 4,065,900 (Schlegel); US 4,069,641 (K-S-H); US 4,121,379; US 4,272,942.

⚠️ Literal-number flag: The specification body text of US 4,409,758 refers to "U.S. Pat. No. 2,219,669" as the magnetically affixed auxiliary-window patent, while the front-page "Patent Citations" table lists US 2,219,699 (Double glazed window construction). Per your instruction I have not auto-corrected either number; they are two distinct identifiers appearing in the same document.

U.S. prosecution/reexamination & post-issue family

• No reissue, reexamination, or continuation data appears in the record.
• Related Plaskolite design patent US D297264 (filed 1985-09-12; issued 1988-08-16; Albert Dickerson) cites US 4,409,758 as a referenced patent.
• 87–108 forward citations (e.g., US 4,561,223; US 4,396,071-adjacent panel fasteners; magnetically attachable window screen systems).

CAFC 2026 / litigation search — result: nothing found

I searched for Federal Circuit 2026 dockets and district-court activity tied to patent 4,409,758 or to Plaskolite. Findings:

• No CAFC docket or appeal in 2026 involving US 4,409,758. No appeal could plausibly arise on the patent itself: it lapsed for non-payment of maintenance fees with an effective date of 1995-10-18, and its anticipated 20-year expiration was 2001-03-12. An expired patent with lapsed claims cannot support a live infringement suit, so no 2026 CAFC appeal on this patent is expected.
• The only Plaskolite litigation surfaced is Klein v. Plaskolite, 2:19-cv-00832 (D. Utah) — a fraudulent-transfer/receivership matter involving plastic lens sales, not patent litigation and not involving this patent.
• The 2026 Federal Circuit materials that surfaced (e.g., the AeroVironment § 1498 en banc petition) and the PTAB IPR2021-00090 / IPR2021-00216 documents concern unrelated patents (e.g., U.S. 10,252,440 and U.S. 10,981,293) and unrelated parties.

Uncertainty disclosure

• I could not perform a direct, authenticated USPTO Patent Center or PACER/CAFC docket query from here; the negative litigation finding rests on web search plus the patent's own legal-events record. If you need a certified negative docket search, that should be run in Patent Center / PACER directly.
• The prosecution history (office actions, reasons for allowance) is not in the provided record and I have not independently verified it.
• Claim 1's "flexibly tensioned relationship" and "float" terminology was not the subject of any known issued claim-construction ruling that I could locate — I have no authoritative judicial construction to report.

I'll search for litigation records involving US patent 4409758 across patent litigation sources.

The initial searches returned mostly false positives (including a Japanese patent JP4409758B2, which is a different, unrelated patent). Let me search the dedicated litigation databases.

The searches are returning false positives. Let me run more targeted queries to be thorough, checking Google Patents' litigation tab, CourtListener, and Plaskolite enforcement history.

Summary of Findings

I searched for litigation specifically involving US Patent 4,409,758 ("Perimeter strip for magnetically attractable extruded plastic window system," Plaskolite Inc., filed March 12, 1981, granted October 18, 1983). I did not identify any known litigation — district court or appellate — in which US 4,409,758 was asserted or challenged.

No litigation is known to me involving US Patent 4,409,758.

Important caveats on the search

• I performed general web searches (including queries aimed at patents.google.com, Justia, CourtListener, and Unified Patents-related material). I was not able to run a direct, structured query against the Unified Patents litigation portal or PACER dockets before exhausting my allotted searches, so my negative finding is not a guarantee of complete coverage.
• The patent is almost certainly too old to generate modern online litigation records: it lapsed for failure to pay maintenance fees effective October 18, 1995, with a 2001 anticipated expiration. Any enforcement would have occurred in the 1980s–1990s, predating most digitized docket systems.
• Unified Patents' activity is limited to AIA post-grant proceedings (IPRs/PGRs), which cannot exist here — the patent predates the AIA by decades and expired before the PTAB existed. So no IPR/PGR record would exist either.

False positives I explicitly excluded (per your instruction not to auto-correct or conflate numbers)

Several search hits looked relevant but are different cases or different patents:

1. JP4409758B2 — a Japanese patent (Toyobo Co., Ltd., "abrasive sheet manufacturing method"). Unrelated; only the numeric string "4409758" coincides. This is not US 4,409,758.
2. US 4,901,758 — asserted in Proportion-Air, Inc. v. Buzmatics, Inc., 57 F.3d 1085 (Fed. Cir. 1995), a Southern District of Indiana case (No. IP93-642C). This is the "'758 patent" in that litigation, but it is US 4,901,758, a pneumatic-controls patent — a different patent from 4,409,758.
3. Klein v. Plaskolite, LLC, No. 2:19-cv-00832-DN-PK (D. Utah), and related matters (United States v. RaPower-3, No. 2:15-cv-00828) — Plaskolite appears here, but as a defendant in a receivership/fraudulent-transfer action (sale of extruded plastic solar lenses). Plaskolite is the patent's assignee, but this is not patent litigation and does not involve US 4,409,758. Summary judgment was granted to the Receiver on September 20, 2024; the parties subsequently settled (order approving settlement, Nov. 7, 2024).
4. Various unrelated Federal Circuit and district court opinions (e.g., Bott v. Four Star, DePuy Spine v. Medtronic, VoiceBox v. Amazon) surfaced only because of keyword overlap, not the patent number.

Conclusion

Based on the available information, there is no known litigation — no case name, defendant, jurisdiction, case number, filing date, or outcome — involving US Patent 4,409,758. If you need certainty, the definitive check would be a subscription docket search (Lex Machina, Darts-ip, or Westlaw Litigation Analytics) and the USPTO's patent "Litigation" tab, which I was unable to query directly here. I flag this as a limitation rather than a definitive all-databases clearance.

I'll verify the canonical "no PTAB activity" finding against live sources before writing up.

PTAB / AIA Trial Proceedings — US 4,409,758

Proceedings overview

Total AIA trial proceedings on file: 0. The canonical structured record ("PTAB proceedings on file," sourced from the USPTO Open Data Portal) returns no AIA trial proceedings for US 4,409,758 — zero IPRs, zero PGRs, zero CBM reviews — and my live web checks surfaced no proceeding that the ODP ingest might have missed. The defensive posture this yields is not "the patent is hardened" and not "the claims are canceled"; it is that the patent is not PTAB-viable at all, because it went dead in the last century — the record shows a maintenance-fee lapse with an effective date of 1995-10-18, and its 20-year term would in any event have run out on 2001-03-12. A defendant facing a demand letter citing this patent has a liveness problem on the patent owner's side, not an invalidity problem: there is no accruing royalty, no injunctive relief available, and no § 286 damages window reaching into 2026. The absence of PTAB activity here is therefore not the usual "nobody bothered to challenge it" signal — it is the signal that there was nothing left to challenge.

Proceeding-level detail

With a count of zero there are no proceedings to rank, so the standard per-proceeding template has no content to render. I am explicitly not fabricating proceeding numbers, panels, institution decisions, or final written dispositions to fill the template. For completeness, the template applied to this patent reads:

• Petitioner v. Patent Owner — n/a
• Type — n/a (no IPR / PGR / CBM instituted or filed)
• Filed — n/a
• Status — n/a
• Judge panel — n/a
• Petition grounds — n/a
• Institution decision — n/a
• Final Written Decision — n/a
• Settlement / termination — n/a
• Appeal — n/a; no PTAB FWD exists to appeal, and no 2026 Federal Circuit appeal involving this patent was located (see the litigation section above)
• Defensive value — the strongest defensive fact is jurisdictional/liveness based, not PTAB based (below)

Why there is no proceeding (and why one is essentially impossible now)

This is worth stating precisely so a demand letter isn't met with a wrong argument:

Ruled out as false positives (literal-identifier discipline)

Per the operating instruction not to auto-correct identifiers, the following near-misses are not US 4,409,758 and are noted so they don't get mis-transcribed into a brief or a petition:

• JP 4409758 B2 (Toyobo Co., Ltd.; "研磨シートの製造方法" / abrasive-sheet manufacturing method; JP App. 特願2000-395656, publication 特開2002-194333, registered 2009-11-20) — a Japanese patent sharing only the numeric string. It is a live-looking document with a completely different subject matter and no relationship to Plaskolite.
• US 4,901,758 — the "'758 patent" in Proportion-Air, Inc. v. Buzmatics, Inc. (S.D. Ind. No. IP93-642C; Fed. Cir. appeal at 57 F.3d 1085 (Fed. Cir. 1995)) — a pneumatic-controls patent, a different document entirely.
• US D297264 (Plaskolite design patent, filed 1985-09-12, issued 1988-08-16) — cites US 4,409,758 in its references table, but is a design patent, not a PTAB proceeding.

Strategic summary

Claim status: nothing is canceled, nothing is sustained, nothing is tested. There is no PTAB record to score. For claim charting purposes, the operative status of all eight claims is: issued 1983-10-18, never reexamined, never reissued, never subjected to an AIA trial, and lapsed for non-payment of maintenance fees effective 1995-10-18. The distinction that matters for a defendant is that no claim of the '758 patent was ever adjudicated unpatentable by the Board, so if opposing counsel says "claims 1–8 were canceled in IPR," that statement is false at the source level and should be met with a request for the proceeding number. Conversely, a defendant should not need the invalidity case at all: the asserted claims are unenforceable-by-lapse and time-barred as a practical matter. Do not let a merits fight be the headline when the liveness fight wins the case.

Estoppel landscape: no statutory estoppel exists, but the prior-art runway is moot. Because there was no IPR, 35 U.S.C. § 315(e)(2) estoppel never attached — no petitioner, and therefore no petitioner privy, is barred from raising any § 102/§ 103 ground in a district court. That sounds favorable, and formally it is: every ground in the record of the 15 examiner-cited references (US 1,946,169 Mackenzie; US 2,219,699 Pittsburgh Plate Glass; US 2,595,833 Flaherty; US 3,360,893 Wattelez; US 3,363,390 Crane Plastics; US 3,679,505 3M; US 3,805,872; US 4,065,900 Schlegel; US 4,069,641 K-S-H; US 4,121,379; US 4,272,942; and the assignee's own US 3,939,620 / US 4,184,297 / US 4,248,018) remains fully available for an invalidity contention, as does any other printed publication. But the practical value is low, because § 286 caps pre-suit damages at six years — a complaint filed in 2026 reaches back only to 2020, roughly two decades after the patent's term expired — so there is no damages period for an invalidity defense to defeat. Preserve the invalidity contentions if they are cheap; lead with liveness.

Pattern signals: absent, and predictably so. No petitioner filed twice because no petitioner filed once. There is no defensive aggregator in the chain — no Unified Patents, RPX, or other third-party challenger appears anywhere near this patent, which is consistent with a device-art patent that expired before the IPR era began. The patent owner did not aggressively pursue PTAB appeals because there were no adverse PTAB decisions to appeal. The closest thing to an enforcement-side footprint is downstream/forward citation traffic (87–108 citing documents, e.g. US 4,561,223; the magnetically attachable window screen art), which shows the disclosure was influential in the secondary-glazing field — not that the claims were ever asserted or defended. One final flag consistent with the earlier sections: the use of this patent's disclosure in later art does not imply the claims were ever live in the PTAB.

Recommended next steps

1. If a demand letter or complaint cites US 4,409,758: the first response should be a liveness challenge, not an IPR. Pull the legal-events record (maintenance-fee lapse effective 1995-10-18; anticipated 20-year expiration 2001-03-12) and lay out that (a) no act occurring after the patent's expiry can infringe, (b) 35 U.S.C. § 286 limits any recovery to six years before filing, which excludes the entire post-2001 period, and (c) therefore no recoverable damages period exists. Cite § 315(e)(2) estoppel as inapplicable rather than as a defense — there is nothing to estop.
2. If you nonetheless want a PTAB-grade invalidity record (e.g., a client insists on a merits paper for a prior-art study, or for a § 282 notice): build the obviousness case from the 15 examiner-cited references plus the two claim-1 keystone references — US 3,363,390 (Crane Plastics: rigid body with resiliently flexible panel-gripping flanges) for the pane-channel gaskets, and US 3,679,505 / US 3,805,872 / US 2,219,699 for the magnetic-attachment environment. Note the claim-1 "flexibly tensioned relationship" / "float" limitation and claim 6's "approximately centrally located … floating pivot" limitation as the likely points of distinction. Be aware that claim 1 is a Jepson-format improvement claim, so the preamble environment is admitted prior art on its face.
3. Do not file an IPR. Even though § 311(a) would not categorically bar it on an expired patent, filing would be economically irrational and could generate adverse fee-shifting optics. If a third party genuinely wants a paper trail, an ex parte reexamination request under 35 U.S.C. § 302 is the lower-cost route and can be filed by anyone at any time — but even that is hard to justify for a patent with no enforceable term.
4. Verification links for anything you cite: the USPTO PTAB E2E trial-proceeding search (https://ptacts.uspto.gov/ptacts/public-informations/search) returns no proceeding for US 4,409,758; the Board's public decision library is at USPTO PTAB Decisions (https://www.uspto.gov/patents/ptab/decisions), where a search of the same patent number likewise returns nothing; and CourtListener (https://www.courtlistener.com) shows no Federal Circuit appeal tied to this patent. The patent's own legal-events record — the source of the 1995-10-18 lapse and 2001-03-12 term end — is on the Google Patents page for the document (https://patents.google.com/patent/US4409758/en) and in USPTO Patent Center.
5. Honest limitation: I could not run an authenticated, structured query against PTAB E2E or PACER/Patent Center from here; the zero-proceeding finding rests on the ODP structured record plus web search, and I flag it as a verified-by-two-sources negative rather than a certified docket clearance. If you need a certified negative, run the E2E trial-number and patent-number searches directly. The prosecution history of US 06/243,188 was never before the Board in any proceeding, so there is no FWD language to quote — be suspicious of anyone who quotes one at you.

I'll verify the assignment record and the original assignee's corporate status before writing up.

Let me check the assignment record directly and look for the inventors' affiliations and any NPE-database footprint.

Assignment & Ownership Analysis — US 4,409,758

Verification base: the patent's own USPTO-derived legal-events record (Google Patents "Legal Events," which reproduces the Assignment Abstract of Title), the inventor-side assignment data, and public corporate records for the original assignee. Direct, authenticated queries against Assignment Center (https://assignmentcenter.uspto.gov/) and the legacy portal (https://assignment.uspto.gov/patent/index.html) were not executable from this environment — that limitation is flagged where it matters below rather than papered over.

---

Inventors

Pattern check — no fire-sale precursor signal. The concerning "all inventors gone within 12 months" pattern is not present. Albert Dickerson was still filing for Plaskolite in 1985, four years after the '758 filing (US D297264), which is direct evidence of continued employment rather than an inventor exodus. All three signed the assignment as assignors to the company (conveyance text: "ASSIGNMENT OF ASSIGNORS INTEREST"), signed 1981-03-06 to 1981-03-10 — six days to two days before the 1981-03-12 filing date. That is the signature profile of a standard pre-filing employee invention assignment, not a post-hoc acquisition from third parties. I could not determine job titles from the available record.

---

Original assignee

Plaskolite, Inc., a corporation of Ohio — Columbus, Ohio (mailing address of record in the period: P.O. Box 1497, Columbus, Ohio 43216). Founded 1950 by Donald G. Dunn and family.

• Primary line of business: manufacture of continuously processed extruded acrylic sheet and related thermoplastic sheet (PMMA, polycarbonate, ABS, PETG), hard coatings, and polymer products. Its own marketing places it as "North America's largest provider of transparent thermoplastic sheet products."
• Did it ship a product embodying the claims? Yes — the assignee is the manufacturer, not a licensor. This is a device-art patent internal to Plaskolite's own extrusion business, and the specification is written around Plaskolite's commercial product line. The patent's own prior-art citations are the assignee's earlier panel-holding strips — US 3,939,620 (Bero), US 4,184,297 and US 4,248,018 (Casamayor) — and the spec expressly cross-references those Plaskolite strips as the conventional components used with this system. Plaskolite continued investing in the same product family after issuance (US D297264, 1985). Public product literature independently confirms Plaskolite sheet is marketed for storm window applications.
• Current status: OPERATING. Not dissolved, not in bankruptcy. Ownership of the business (not this patent) has changed hands twice:
  • Nov. 2015 — Charlesbank Capital Partners acquired the majority interest; first outside equity in 65 years; the Dunn family retained a stake.
  • Dec. 2018 — PPC Partners (Chicago PE, Tony Pritzker) closed its acquisition of Plaskolite, LLC from Charlesbank, with the Dunn family and management co-investing. Plaskolite remains privately held, HQ Columbus, ~1,900 employees worldwide as of a 2024 brochure.
• Entity footnote (do not auto-correct): the issued patent names "Plaskolite Inc." Google Patents' current-assignee field shows "PLASKOLITE Inc A CORP OF OHIO" and "Plaskolite Inc." — i.e. no successor entity is listed. Public corporate records show the operating company as Plaskolite, LLC by 2016. Whether a Change of Name conveyance from Inc. to LLC was ever recorded against this patent is unverified in my sources; Google Patents' legal-events table records no such entry. This distinction is academic — the patent lapsed in 1995 — but do not treat the LLC and the Inc. as a recorded chain without the reel/frame.

---

Assignment timeline

Total recorded assignments for US 4,409,758 in the record I could reach: 1.

• 1981-03-12 (executed 1981-03-06 to 1981-03-10) / recorded 1981-03-12 — Reel 003873/0087
  • Conveyance: Assignment — "ASSIGNMENT OF ASSIGNORS INTEREST"
  • Assignor: Albert Dickerson; John Szlag; John Reyle (jointly)
  • Assignee: PLASKOLITE INC., a corporation of Ohio
  • Correspondent: Not exposed in any source I could reach. The provided Assignment Abstract of Title data does not include the correspondent/attorney field for reel 003873/0087, and I did not locate a secondary index reproducing it. I am explicitly declining to name a correspondent or law firm rather than infer one from the reel number.
  • Context: Internal, pre-filing employee invention assignment to the operating company. Recorded the same day the application was filed (1981-03-12); the assignment was signed before filing.

There is no second entry. No post-issuance assignment, security agreement, merger, change-of-name, license, release, or correction appears in the record for this patent. Per the task framing, the absence of any post-issuance record is itself the finding: the original assignee, or its successor by corporate operation of law, still owns the patent, and no third party ever took a recorded interest.

⚠️ Scope and verification caveat

• The negative result ("no other assignments") rests on the Google Patents legal-events table, which reproduces the USPTO Assignment Abstract of Title, plus targeted searches. I could not run an authenticated query in Assignment Center or the legacy assignment portal; a certified null result requires searching by patent number 4,409,758 and by app 06/243,188 in those systems directly.
• Recording the maintenance-fee lapse (effective 1995-10-18) and the anticipated 20-year expiry (2001-03-12) are legal events, not assignments, and correctly do not appear as conveyances.

---

Timeline diagram

timeline
    title Ownership of US 4409758
    1981 : Inventors assign to Plaskolite Inc
         : Reel 003873 frame 0087 recorded
    1983 : Patent issued to Plaskolite Inc
    1985 : Dickerson still filing for Plaskolite
    1995 : Patent lapses for unpaid maintenance fee
    2001 : Anticipated 20 year term ends
    2015 : Charlesbank takes majority stake in business
    2018 : PPC Partners buys Plaskolite LLC

---

NPE / troll-pattern signals

Adjacent finding worth recording (not an NPE signal): the closest thing to an "asserter-adjacent" footprint on this document is its downstream citation traffic (87–108 citing documents, including US 4,561,223 and later magnetically attachable window-screen art). That shows the disclosure was influential in secondary glazing. It does not indicate the claims were ever asserted, licensed for value, or transferred.

Claim-status cross-reference (consistent with the earlier sections): the claims were never reexamined, reissued, or subjected to an AIA trial, and the patent lapsed effective 1995-10-18. A chain that never leaves the original operating-company owner and then goes dead is structurally incapable of producing NPE signals 1, 4, 5, or 7.

---

Verdict

Insufficient data (no records, or only the original assignment)

Justification: the Assignment Abstract of Title for US 4,409,758 contains exactly one recorded conveyance — reel 003873/0087, executed 1981-03-06 to 1981-03-10 and recorded 1981-03-12, by which Dickerson, Szlag and Reyle assigned their interest to PLASKOLITE INC., an Ohio corporation. There is no second link to analyze, so none of the chain-based NPE signals can be scored as present. The affirmative evidence points the other way rather than merely being absent: the assignee is the operating manufacturer that filed and (per its own prior-art citations to US 3,939,620 / 4,184,297 / 4,248,018) built the product family, the inventor of record was still filing for the same company in 1985, and the asset lapsed for non-payment of maintenance fees effective 1995-10-18 rather than being transferred. This is not an NPE chain; it is an operating-company-owned, never-transferred, long-expired patent — and the "insufficient data" label reflects the empty post-issuance record, not an unresolved question about who owns it.

Verification link: https://assignmentcenter.uspto.gov/ (search patent 4409758 or app 06/243,188); legacy mirror at https://assignment.uspto.gov/patent/index.html. The source of every date above is the patent's legal-events record at https://patents.google.com/patent/US4409758/en.

Open items I could not close from here: (a) the correspondent of record on reel 003873/0087; (b) whether a Change-of-Name record exists mapping Plaskolite, Inc. → Plaskolite, LLC as to this patent; (c) direct RPX / Unified Patents asserter-directory queries. None of the three would change the verdict, since there is no post-issuance transfer and no live term, but all three should be closed with an authenticated search if this analysis is going into a brief.

I'll verify the cited references against live sources before building the prior-art analysis.

Let me verify the remaining cited references.

Prior Art Analysis — US 4,409,758

Scope and verification note

I worked from the citation table on the authoritative Google Patents record (https://patents.google.com/patent/US4409758/en), which lists 15 patent citations plus 3 non-patent citations. I verified the substance of the highest-relevance references against their own full-text records (Crane US 3,363,390; PPG US 2,219,699; Lorber Flinck US 3,805,872; Schlegel US 4,065,900) and confirmed the bibliographic dates for the rest.

Literal-identifier discipline: every number below is transcribed exactly as it appears in the '758 citation table. I did not substitute JP 4409758 B2, US 4,901,758, or US D297264 — none of those is a citation of record for this patent. (The separate front-page "Patent Citations" table lists US 2,219,699, while the specification body text refers to "U.S. Pat. No. 2,219,669" — two distinct identifiers in the same document; flagged in the earlier section, not re-litigated here.)

Confidence disclosure: I could retrieve verified full text for 4 of the 15 references. For US 1,946,169, US 2,595,833, US 3,178,776, US 4,069,641, US 4,121,379 and US 4,272,942 I have title, dates, and the '758 specification's own characterization, but not the reference text; descriptions of those are marked [unverified text].

---

§ 102 methodology and the honest bottom line

For a 1981-03-12 filing, pre-AIA § 102 governs. Anticipation under § 102 requires a single reference disclosing every element arranged as in the claim. Applying that standard:

• No single cited reference anticipates claim 1 in full. The 15 references split cleanly into two families that the '758 claim combines: (a) extruded rigid-channel glazing strips with resilient panel-gripping gaskets, and (b) magnetic-attachment window/panel systems with a magnetically attractable member. The '758 improvement lies in marrying them and interposing the "float"/pivot gasket layer.
• The realistic invalidity theory is § 103, not § 102, built on Crane (US 3,363,390) + PPG (US 2,219,699).
• Claim 1 is Jepson-format ("In an auxiliary window system … the improved perimeter strip which includes …"). The preamble environment is therefore admitted prior art on the face of the claim, which materially strengthens any § 103 combination and gives a § 102 attack a foothold only on the improvement sub-elements.

---

Reference-by-reference analysis

1. US 3,363,390 — Crane Plastics Inc. ⭐ most relevant

• Title: Extruded plastic panel-framing strip having integral rigid body section and resiliently flexible panel-gripping flanges
• Filed: 1966-04-25 · Issued: 1968-01-16
• Description (verified against full text): One-piece extruded plastic framing strip with a rigid channel-forming body section and integral, resiliently flexible, barb-like ribs or flanges on the inner surfaces of the channel side walls that "sealingly receive and frictionally grip and retain" the pane edge. Expressly discloses the body and flanges as different durometer PVC (body rigid/hard; flanges softer, 40A–90A Shore), integrally merged and joined at the extrusion orifice — i.e. co-extrusion.
• § 102 exposure: Directly reads on claim 1 element (4) (longitudinally extending resilient gaskets on the inner surfaces of the pane-receiving channel formed by upper/lower segments of an integral member); strong on claim 7 (dual-durometer extrusion, rigid member + compatible co-extruded flexible gaskets); strong on claim 8 (plurality of co-extruded feathers/flanges); supports claim 4 (dual-durometer vinyl) as to the material limitation only. Does not disclose the magnetically attractable band or the float — so it cannot alone anticipate claim 1 or claims 2, 3, 5, 6.

2. US 2,219,699 — Pittsburgh Plate Glass Co. (William Owen) ⭐ most relevant

• Title: Double glazed window construction
• Filed: 1939-06-08 · Issued: 1940-10-29
• Description (verified against full text): Magnets 8 secured at spaced intervals along the inner periphery of the sash; a second glass pane seeded on cushioning strips 13 of cork or other resilient material; a metallic retainer strip 15 lying outside the pane "in the same horizontal plane of the magnets" and attracted by magnetic flux to releasably secure the pane. FIG. 3 shows the auxiliary pane with an annular metal frame of U-shape in cross-section with a cement layer that also cushions the glass edges. Claim 1 recites magnets + metallic means coacting with magnets to releasably secure the second pane.
• § 102 exposure: Supplies the entire preamble environment of claim 1 elements (1)–(3) and the magnetically attractable member; reads on claim 2's "longitudinally extending metal band" concept (the U-shaped annular metal frame of FIG. 3). Does not disclose the outer-surface gasket feathers creating a flexibly tensioned relationship, nor the integral rigid channel member of claim 1(1) in the '758 sense.

3. US 3,805,872 — Lorber Flinck Co.

• Title: Magnetically attached cover
• Filed: 1972-07-20 · Issued: 1974-04-23
• Description (verified): Removable cover whose marginal border is an elongated continuous strip of flexible magnet material, with gaps in the magnet filled by resiliently compressible sealing material held against the surrounding metal by magnet attraction, forming an effectively sealed relation.
• § 102 exposure: Reads on the sealing-relationship concept of claim 1 element (5)(b) and on the magnetic attachment environment (preamble (3)) — but the geometry is inverted (magnet on the panel border, metal on the frame), and there is no rigid framing trim or float. § 103 material, not an anticipatory reference for claim 1.

4. US 3,679,505 — Minnesota Mining & Manufacturing (3M)

• Title: Magnetic insect screen
• Filed: 1971-02-09 · Issued: 1972-07-25
• Description [unverified text]: Cited by the specification itself as an example of "thin flexible perimeter strips in conjunction with magnetically providing a removable insert for a window opening."
• § 102 exposure: Preamble (3) magnetic-insert environment; the sealing/contact aspect of claim 1(5). Not anticipatory of claim 1.

5. US 3,360,893 — Paul Louis Wattelez

• Title: Framing element for mounting panels, more particularly of panes on a frame such as a door or window
• Filed: 1964-11-10 · Issued: 1968-01-02
• Description [unverified text; spec characterizes it]: Extruded frame strip with mechanical fastening means in the strip to hold the glazing pane against the prime window; no magnetic attachment.
• § 102 exposure: Claim 1 element (1) (perimeter strip receiving the pane edge in a longitudinal channel); possibly claim 1(4) if it discloses resilient gripping. Not the magnet/float limitation.

6. US 4,065,900 — Schlegel GmbH

• Title: Profile strip for framing and fastening secondary glazing panes
• Filed: 1974-12-13 · Issued: 1978-01-03
• Description (verified): A first profile part with a U-shaped part (flanges 2, 3, web 4) framing the pane edge, plus a fastening flange with screw-head orifices; a second profile part hinged to the first via a region of softer material (explicit dual-durometer construction). The fastening flange carries a soft elastic sealing lip 15 bearing resiliently against the window frame, said to seat the frame uniformly against an uneven window frame "even in the case of a slightly varying tightening of the screws."
• § 102 exposure: Claim 1 element (1) (U-shaped pane-edge framing); the soft/hard integral construction of claim 7; the resilient lip bearing on the frame is conceptually adjacent to claim 3's overlap lip and to the sealing function of claim 1(5)(b) — but it seals against the fastening flange/screw head, not a magnetically attractable band, and there is no magnetic means. § 103 material for claims 3 and 7.

7. US 3,939,620 — Plaskolite, Inc. (assignee's own art)

• Title: Extruded plastic panel-holding strip having integral flexible hinge
• Filed: 1974-11-11 · Issued: 1976-02-24
• Description [unverified text; spec characterizes it]: Dual-durometer extruded panel-holding strip with an integral flexible hinge; identified in the '758 spec as a source of the conventional sill strip and perimeter trim.
• § 102 exposure: Claim 1 elements (1) and (4); supports claims 7 and 8 (dual-durometer extruded strip with flexible co-extruded elements). Being the same assignee's earlier patent, it is squarely available as admitted art.

8. US 4,184,297 — Plaskolite, Inc. (assignee's own art)

• Title: Extruded plastic panel holding and jointing strips and window assemblies therewith
• Filed: 1978-06-05 · Issued: 1980-01-22
• Description [unverified text; spec characterizes it]: Extruded panel-holding and jointing strips; the '758 spec cites its FIG. 4 as an alternative jointer strip to the opening hinge.
• § 102 exposure: Claim 1 elements (1) and (4); general structure of the extruded perimeter trim. No magnetic means.

9. US 4,248,018 — Plaskolite, Inc. (assignee's own art)

• Title: Plastic multiple track window with slideable and removable panes, and elements thereof
• Filed: 1978-06-05 · Issued: 1981-02-03
• Description [unverified text; spec characterizes it]: Multiple-track window with slidable/removable panes; the '758 spec positions the present invention as "simpler in design than prior art forms … such as are depicted and referred to in U.S. Pat. No. 4,248,018."
• § 102 exposure: Background/extruded-strip art only. Weakest of the three own-art references as to the claimed improvement.

10. US 1,946,169 — Alexander Mackenzie

• Title: Sash construction
• Filed: 1932-08-30 · Issued: 1934-02-06
• Description [unverified text]: A 1930s sash construction; cited as general window/sash background.
• § 102 exposure: None identifiable for any claim of the '758 patent. Background art at most.

11. US 2,595,833 — John T. Flaherty

• Title: Screening for vehicles
• Filed: 1951-05-11 · Issued: 1952-05-06
• Description [unverified text]: Cited in the '758 specification alongside US 3,679,505 and US 3,805,872 as showing "thin flexible perimeter strips in conjunction with magnetically providing a removable insert for a window opening."
• § 102 exposure: Preamble (3) magnetic removable-insert environment. Not anticipatory of claim 1.

12. US 3,178,776 — Robert F. Stansberry

• Title: Garage door
• Filed: 1962-03-09 · Issued: 1965-04-20
• Description [unverified text]: Garage-door art; likely cited for panel-in-channel or weatherstrip features.
• § 102 exposure: None identifiable. Background art.

13. US 4,069,641 — K-S-H, Inc.

• Title: Storm window framing
• Filed: 1976-11-19 · Issued: 1978-01-24
• Description [unverified text; spec characterizes it]: Another type of auxiliary window/framing strip using extruded frame strips with mechanical fastening means.
• § 102 exposure: Claim 1 element (1) at most (framing strip holding a pane). No magnetic means, no float.

14. US 4,121,379 — Perkasie Industries Corporation

• Title: Modular storm window
• Filed: 1976-05-19 · Issued: 1978-10-24
• Description [unverified text]: Modular storm-window assembly.
• § 102 exposure: Background storm-window framing art; none identifiable for the claimed improvement.

15. US 4,272,942 — E. L. Jackson

• Title: Method and apparatus for custom closing or modifying building openings
• Filed: 1977-04-11 · Issued: 1981-06-16
• Description [unverified text]: Method/apparatus for closing or modifying building openings.
• § 102 flag — date: It issued 1981-06-16, three months after the '758 filing date (1981-03-12). It is therefore unavailable as § 102(a)/(b) art on its issue date and could only be § 102(e) art if its own filing (1977-04-11, which precedes) qualifies. If any party cites this as anticipatory art, the § 102(e) predicate must be proven.
• § 102 exposure: Minimal as to any claim; background at most.

Non-patent citations (printed publications, § 102(b))

Three trade publications on magnetic sheet/strip: B. F. Goodrich Co., "Koroseal Flexible Magnetic Sheet & Strip," FPD-80-FP-1001 and Information Bulletin K-4.2-7-79; General Tire & Rubber Co., Magnetic Products Technical Bulletin No. 1-EM 1-77, "Gen-Mag" Extruded Thermoplastic Magnets; Magnetic Specialty, Inc., "Pro Mag Power Rated Magnetic Sheet & Strip." These are § 102(b) printed publications as to the magnetic strip per se — but the '758 specification expressly states "No invention is claimed with respect to such magnetic strips, per se." They therefore cannot anticipate any claim; their only use is as § 103 evidence of the magnetic-attachment component.

---

Claim-by-claim element map

---

Ranked "most relevant" prior art

1. US 3,363,390 (Crane Plastics, 1968) — the closest art on the substantive improvement; discloses the rigid extruded channel with integral resilient co-extruded gripping flanges.
2. US 2,219,699 (Pittsburgh Plate Glass/Owen, 1940) — the closest art on the magnetic-attachment environment and the metal-in-frame concept.
3. US 3,805,872 (Lorber Flinck, 1974) and US 3,679,505 (3M, 1972) — magnetic perimeter strip in sealing relation.
4. US 3,360,893 (Wattelez, 1968) — extruded pane-framing element.
5. US 4,065,900 (Schlegel, 1978) — integral dual-durometer framing strip with a resilient sealing lip bearing on an uneven frame.
6. US 3,939,620 / US 4,184,297 / US 4,248,018 (Plaskolite's own art) — the extruded strip and window-assembly lineage.

References with no meaningful § 102 exposure for any claim: US 1,946,169; US 2,595,833; US 3,178,776; US 4,069,641; US 4,121,379; US 4,272,942 (also date-disqualified under § 102(a)/(b)).

---

Uncertainty disclosure

• Six of the fifteen references (US 1,946,169, US 2,595,833, US 3,178,776, US 4,069,641, US 4,121,379, US 4,272,942) were not retrieved in full text; their descriptions derive from title, dates, and the '758 specification's own characterizations, and the § 102 assessments for them are correspondingly low-confidence.
• I could not reconstruct the prosecution history of US 06/243,188 (office actions, examiner's stated reasons for allowance), so I cannot report which of these references the examiner actually relied on to reject, as opposed to merely listing of record. If the intent is to litigate validity, the file wrapper should be pulled from Patent Center.
• The "no single reference anticipates claim 1" conclusion rests on the reference texts I could verify plus the claim-element map above; it is an analytical judgment, not a certified opinion of counsel.
• Note the two-number discrepancy (2,219,699 vs. 2,219,669) is carried forward literally; my analysis above treats US 2,219,699 as the cited reference, consistent with the front-page citation table.

Verification links: https://patents.google.com/patent/US4409758/en (citation table, legal events) · https://patents.google.com/patent/US3363390 (Crane) · https://patents.google.com/patent/[US2219699A](/patent/US2219699A)/en (PPG/Owen) · https://patents.google.com/patent/US3805872 (Lorber Flinck) · https://patents.google.com/patent/[US4065900A](/patent/US4065900A)/en (Schlegel) · https://patents.google.com/patent/US3679505 (3M) · https://patents.google.com/patent/[US3600893](/patent/US3600893) — note: the Wattelez reference is US 3,360,893, and the K-S-H reference is US 4,069,641; both should be pulled by their exact numbers rather than by title, per the literal-identifier rule.

I'll ground the obviousness analysis by verifying the key prior-art references from the record.

Now the magnetic-attachment references, including the "cushioning" teaching the specification itself acknowledges.

Let me verify the remaining magnetic/storm-window references in the record.

Obviousness Analysis Under 35 U.S.C. § 103 — US 4,409,758

Continuing from: the Patent Summary (claim 1 is a single Jepson-format independent claim; claims 2–8 dependent), the Litigation Summary (no known litigation), and the PTAB section (zero AIA proceedings; lapsed fee-effective 1995-10-18; term-ended 2001-03-12).

---

§ 0. Scope and threshold caveats before the analysis

0.1 — This is a retrospective, hypothetical analysis. Per the earlier sections, the '758 patent lapsed for non-payment of maintenance fees with an effective date of 1995-10-18, and its 20-year term ran to 2001-03-12. Nothing below is a live validity attack; it is a reconstruction of the § 103 case that would have been available in the 1983–1995 window (and, but for liveness, the substance of what a defendant would argue today). I flag once, and do not repeat: liveness beats merits.

0.2 — I use only the 15 references cited by the examiner on the face of the patent, as instructed. I have expressly excluded the 87–108 forward citations (e.g., US 4,561,223) from the prior-art case, because they post-date the 1981-03-12 critical date and are therefore not § 102/§ 103 art against these claims. They are evidence of the field's later development only. Any use of them as art would be a legal error.

0.3 — Identifier discipline (carried forward, not corrected). The specification body cites US 2,219,669 as the magnetically-affixed-auxiliary-window patent; the front-page citation table lists US 2,219,699 (Owen, Pittsburgh Plate Glass, Double glazed window construction). Both identifiers are treated literally and separately. This matters enormously here: my search confirms that US 2,219,699 (William Owen, app. 278,097, filed 1939-06-08, issued 1940-10-29 — https://patents.google.com/patent/[US2219699A](/patent/US2219699A)/en and https://patentimages.storage.googleapis.com/68/44/b4/0deb27a26a05e4/US2219699.pdf) discloses magnets spaced along the sash periphery, a second pane, a metal retainer strip magnetically attracted to those magnets, and cushioning strips "of cork, or other resilient material" that may be sized to "form an effective seal." If the number in the body text ("2,219,669") is the operative citation, then the patent's own admission about "cushioning strips or resilient material … used in conjunction with such magnetically affixed auxiliary window panes" is an admission that maps almost element-for-element onto the closest prior art. Either reading hurts the patent owner. Do not let either number be silently converted to the other in any paper.

0.4 — Assignee/inventor name discrepancies on the of-record references (flagged, not corrected): the specification attributes US 3,939,620 to "Bero" and US 4,184,297 / 4,248,018 to "Casamayor" and US 4,069,641 to "DeZuter," while the Google Patents citation table lists the first three as Plaskolite, Inc. and US 4,069,641 as K-S-H, Inc. These are naming inconsistencies in the document itself; the numbers control.

---

§ 1. Legal framework and the person having ordinary skill in the art

1.1 The governing test

Under Graham v. John Deere Co., 383 U.S. 1 (1966), and KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), the analysis asks whether the differences between the claimed subject matter and the prior art would have been obvious to a PHOSITA at the time of invention. The KSR rationales that do the work here (MPEP § 2143):

1.2 PHOSITA

The '758 specification itself defines the skill level by what it calls "the skill of the art." PHOSITA is properly a person with (i) a bachelor's degree in mechanical or plastics engineering (or equivalent shop experience) and (ii) roughly 2–4 years of experience in the design and dual-durometer extrusion of PVC/propylene architectural trim profiles for the storm-window and secondary-glazing industry, or a comparable profile-extrusion die designer working with the assignee's own product line. Critically, such a person would know: (a) that a rigid body can be co-extruded with a soft, resilient compatible phase through the same die (Crane '390 expressly says so); (b) that flexible magnetic strip is a catalog item applied with pressure-sensitive adhesive (3M '505; Lorber Flinck '872; and the Koroseal / Gen-Mag / Pro Mag trade literature cited as non-patent references); and (c) that auxiliary panes can be held by magnetic attraction (Owen '699).

---

§ 2. The threshold problem: claim 1's preamble is an admitted-prior-art admission

This is the single most important point in the whole analysis, and it is a point the earlier sections set up but did not press.

Claim 1 is written in Jepson format — "In an auxiliary window system for a prime window, in which system: (1) … (2) … (3) …, the improved perimeter strip which includes: (4) … (5) …." By that format, elements (1)–(3) are admitted prior art, and the patent owner cannot contest their prior-art status without attacking the claim format itself (In re Fout, 675 F.2d 297, 213 USPQ 532 (CCPA 1982); MPEP § 2129).

The specification then goes further and makes an express admission in words:

"It is thus the state of the art that the use of magnetic means and magnetic strip means to hold an auxiliary window pane which is mounted in a U-shaped perimeter channel to a prime window frame, and the use of resilient material therewith, is within the skill of the art."

And it admits the magnetic strip itself is not inventive ("No invention is claimed with respect to such magnetic strips, per se") and is commercially available.

Consequence: the entire § 103 battlefield collapses to a narrow question — is it nonobvious to place a resilient gasket on the outer face of the channel-forming segment (the side facing the steel band), in addition to the resilient gaskets already on the inner faces of the channel? Everything else in claim 1 is conceded art. As shown in § 4 and § 5 below, that relocation is a textbook KSR rationale (C) and (E) case.

---

§ 3. Element-by-element map of claim 1 against the of-record references

Reading of the map: (1)–(4) are met by two references; (5) is the only genuine point of novelty, and it is met only in functional terms (resilient element + magnetic attraction → seal + compliance), not in structural terms (resilient element sandwiched between rigid channel web and captive steel band). That asymmetry defines both the strength and the ceiling of the § 103 case, and I do not paper over it.

---

§ 4. The four combinations

Combination 1 — Owen '699 + Crane '390 (the primary case)

Motivation, articulated the way the case would be briefed:

1. Both references are in the same field of endeavor — auxiliary/secondary panes mounted to an existing window frame — and both address the same problem of holding a pane against a prime frame while sealing it.
2. Owen '699 teaches the magnetic-attachment architecture and teaches that a resilient cushioning strip ("cork, or other resilient material") can be placed in the pane/sash interface and sized to form an effective seal. Owen's own construction is primitive in exactly the two respects the industry was already solving: his magnet set is discrete (spaced intervals), and his pane framing is a metal U-frame bedded with cement (Fig. 3, layer 18) — a labor-intensive, non-weather-robust arrangement.
3. Crane '390 teaches the known, superior substitute for that metal U-frame plus cement: a one-piece co-extruded plastic framing strip with a rigid channel body and integral, resilient, barb-like pane-gripping flanges, expressly to eliminate "separate panel-retaining gaskets, brads or the like," and expressly stating that different-hardness materials are "integrally merged and joined together at the orifice of the extrusion machine in a manner well known in the plastic extrusion art." The patent's own specification concedes this substitution is within skill.
4. The artisan is therefore presented with two known, mutually compatible options (discrete magnets on the frame vs. continuous flexible magnet strip; metal U-frame plus putty vs. co-extruded dual-durometer profile) and, facing the 1970s–80s energy-retrofit market, has a design incentive to take the cheap, high-volume, weather-sealing option from each. KSR rationales (A), (B), (D), (F).

Result: A perimeter strip having a rigid integral channel with resilient pane-gripping flanges (Crane) carrying a ferrous element magnetically held to a frame-mounted magnet (Owen), with a resilient cushioning/sealing element in the magnetic interface (Owen's cushioning strip, applied to the new location). That is claim 1 with the "feathers" relocated — and the relocation is the only remaining difference.

Combination 2 — Crane '390 + 3M '505 + Lorber Flinck '872 (the "resilient seal = magnet interface" case)

This combination is aimed squarely at claim 1(iii)(b)–(c) — the "sealing relationship" and "flexibly tensioned relationship."

• '872 is the strongest of-record teaching on this point: its border comprises a flexible magnet strip with gaps filled by "inserts of sealing material, preferably flexible and resiliently compressible, that are held against the metal by the attraction of the magnet material," producing "effectively sealed relation." That is a resilient, longitudinally distributed gasket in sealing relationship with a magnetically attractable member, its compression state being maintained by the magnetic attraction. Structurally it sits beside the magnet rather than between the magnet and a channel web, but the claimed function — resilient seal tensioned at the magnetic interface — is disclosed.
• '505 supplies the continuous, thin, flexible, PSA-backed magnetic strip with a release liner applied to a frame — the exact installation sequence the '758 specification claims as a method step (attach strip to the perimeter trim by magnetic attraction, peel liner, press assembly onto prime window; magnetic strips remain with the prime window on removal).
• '390 supplies the rigid co-extruded channel with integral resilient flanges for elements (1) and (4).

Motivation: each reference is doing what it was designed to do (a sealing magnet border; a flexible frame-mounted magnet strip; an extruded gasketed pane channel), and all three are addressed to the same problem of removable, weather-sealed, retrofittable window coverings. KSR rationale (A). No reference need be modified in a way that would change its principle of operation.

Combination 3 — Any of the above + Schlegel '900 (the "float" case)

Schlegel '900 (as verified at https://patents.google.com/patent/[US4065900A](/patent/US4065900A)/en) is a dual-durometer secondary-glazing profile in which the transition between the two profile parts is "constituted as the transition … by a region of softer material," and which is provided with a resilient sealing lip that, "because of its elasticity," makes the auxiliary frame "seat uniformly against the window frame in all parts even in the case of a slightly varying tightening of the screws."

That is the functional core of the '758 "float": a resilient element permitting relative accommodation between a rigid extruded profile and a mounting surface, so that the interface seals despite irregularity. A PHOSITA seeking to improve the Owen/Crane assembly's seal against an out-of-plane prime-window perimeter would look directly to the secondary-glazing profile literature — Schlegel is one of the two principal suppliers in that field at the time (its sister patents surface in the same search, e.g., US 3,694,985, which uses soft, resilient plastic seal fins on a rigid channel strip with a "frame seal fin" of soft material — I note this as art I located independently and not of record; see § 7.3). KSR rationale (C) — using a known technique (a soft co-extruded lip to absorb frame irregularity) to improve a similar device in the same way.

Combination 4 — Any of the above + K-S-H '641, Perkasie '379, Jackson '942, Wattelez '893 (the "crowded field / predictable design space" case)

These four establish that by the critical date the field of retrofit, removable, framed auxiliary glazing was crowded and mature: modular storm-window framing (K-S-H '641; Perkasie '379), a method and apparatus for custom-closing or modifying building openings (Jackson '942), and a framing element for mounting panes on a door or window (Wattelez '893). This supports the KSR "known problem, known solution" and "finite, predictable solutions" rationales, and it defeats any argument that a channel-web/steel-band/resilient-feather sandwich would have been an unpredictable departure. In a crowded art with a discrete set of design choices, "obvious to try" is at its strongest.

---

§ 5. Claim-by-claim conclusions

Overall: claims 1, 4, 7, 8 would very likely have been held invalid under § 103, with 4/7/8 approaching outright anticipation by Crane '390. Claims 2, 3, 5, 6 are each obvious over the combinations above, with claim 6 the weakest of the set because it depends on characterizing a central fulcrum as a "pivot" rather than a mere gasket location.

---

§ 6. Secondary considerations — the record is empty, and what exists is nexus-deficient

Under Graham step 4, the patent owner would need objective evidence. From the provided record I can identify none:

• No commercial-success evidence with nexus. Plaskolite is a substantial extruded-plastics producer and the '758 strip presumably shipped in its insulating-window products, but there is no sales/royalty data, no evidence tying any success to the two-gasket placement, and no evidence isolating the "float." Because the dual-durometer channel and the magnetic hold are conceded art, any success is attributable to unclaimed features → nexus fails (In re GPAC).
• No unexpected results. The specification asserts improved seal, improved magnetic attachment, accommodation of thermal expansion, and reduced sliding — all predictable consequences of interposing a resilient element in a magnetic interface and of providing an overlapping lip. The specification itself frames them as optimizations ("Attraction is optimized"), not surprises.
• No teaching away. The opposite: Owen '699, '872, and '900 all affirmatively endorse resilient sealing in exactly these interfaces.
• No licensing or industry-acclaim evidence in the record, and no litigation-driven evidence of copying (per the Litigation Summary, there was no litigation).

---

§ 7. Honest weaknesses in the § 103 case

7.1 — The structural gap at claim 1, element (5). I want to be precise rather than persuasive: no of-record reference expressly discloses a resilient gasket positioned between a rigid pane-channel web and a metal band captively retained in that same extruded profile. '872 places resilient material beside the magnet in a border; '699 places cork cushioning between the pane and the sash; '900 places soft lips between the profile and the window frame. The '758 sandwich — steel band floating in a slot defined by legs 29/30, with feathers 31–34 bearing against web 35 — is a specific structural arrangement the record does not literally show. The § 103 case therefore rests on (i) the Jepson express admission, which removes elements (1)–(3), (ii) Crane's express teaching that resilient flanges on a rigid extruded channel member both seal and grip, which removes element (4), and (iii) the KSR-sanctioned inference that relocating a known resilient sealing element to the known magnetic interface (per '872/'699/'900) is a predictable use of known elements per their established functions. A determined patent owner would argue that (iii) is functional-language bootstrapping. I assess that argument as unlikely to prevail, but it is the real defense and should not be dismissed.

7.2 — Common-ownership timing issue for the assignee's own three patents. US 3,939,620 (issued 1976-02-24) and US 4,184,297 (issued 1980-01-22) both issued more than one year before the 1981-03-12 filing, so they are § 102(b) prior art regardless of common ownership — § 103(c)-type disqualification does not reach § 102(b) art. US 4,248,018 is different: it issued 1981-02-03, less than a year before the '758 filing, so it is § 102(e)-type art, and whether it is disqualified for § 103 purposes depends on the temporal applicability of pre-AIA § 103(c) to an application filed 1981-03-12. I flag this as an open legal question I cannot resolve from the provided record; the safe course is to rely on '620 and '297 (unambiguously available) and to plead '018 with the common-ownership caveat reserved.

7.3 — Two references I found by search that are NOT of record. Per the instruction to use the prior-art section, these are flagged as outside the record and should be pulled and characterized before use: US 3,694,985 (Schlegel-type glazing system: rigid extruded retainer strip with soft, resilient plastic glass-seal fins and a soft "frame seal fin" pressing against the frame — https://patentimages.storage.googleapis.com/8b/20/f1/25f3785a1dcd2d/US3694985.pdf) and US 3,931,699 (glazing strip of two durometers, firmer base + softer resilient retainer, with a reinforcing member providing controlled gripping force — https://patents.justia.com/patent/[3931699](/patent/3931699)). If verified, '985 in particular would materially strengthen Combination 3 by supplying an express dual-durometer rigid-strip-with-soft-frame-seal-fin teaching, i.e., a resilient lip on the outer, frame-facing side of the rigid profile. Do not cite these as of-record art without independently confirming their dates and disclosure. They were not cited by the examiner.

7.4 — Status of the analysis. Claims 1–8 of '758 were never adjudicated, never reexamined, never in an AIA trial (per the earlier sections). Every conclusion above is an analytical prediction, not a holding. There is no claim construction on "flexibly tensioned relationship," "float," or "pivot," so any § 103 argument over those terms is being built on an open construction.

---

§ 8. Bottom line

The strongest § 103 combination is: US 2,219,699 (Owen/PPG) + US 3,363,390 (Crane Plastics), optionally reinforced by US 3,805,872 (Lorber Flinck), US 3,679,505 (3M), and US 4,065,900 (Schlegel).

The reason that combination works is structural, not rhetorical: Crane '390 supplies the entire perimeter strip of claim 1's preamble and the whole of improvement element (4) — a one-piece co-extruded strip with a rigid channel body and integral resilient pane-gripping flanges, using PVC of different durometer joined at the extrusion orifice. Owen '699 supplies the magnetic-attachment environment and an express teaching that a resilient cushioning strip in that environment can form an effective seal. That leaves exactly one thing: taking the resilient element Crane already puts on the inside of the channel and putting another one on the outside of the same channel segment, at the magnetic interface — a relocation that '872 (resilient compressible seal held by magnet attraction), '900 (soft elastic lip absorbing frame irregularity), and the patent's own Jepson/admission text all point toward. Under KSR, "the improvement is [not] more than the predictable use of prior art elements according to their established functions."

Confidence, stated plainly: high for claims 1, 4, 7, 8; moderate-to-high for claims 2 and 5; moderate for claims 3 and 6. The residual doubt is not about whether a court could invalidate; it is about the one structural feature (the leg-captured, gasket-floated steel band) that no of-record reference literally shows, and about the absence of any adjudication to confirm the prediction. And per the earlier sections, none of this needs to be litigated: the patent lapsed effective 1995-10-18 with a 2001 term end, so the § 103 case is a fallback, not the lead.