US 1572154

I'll verify against live sources, then summarize.

US 1,572,154 — Verification and Summary

Search coverage note: The number 1572154 was searched literally. USPTO/Google Patents records for this exact number return one document; my search of CAFC 2026 dockets and general litigation sources returned no litigation, IPR, or appeal activity involving this patent. I cannot claim exhaustive docket coverage — I found no affirmative evidence of any CAFC proceeding, but absence of results in the sources I searched is not proof of absence.

Bibliographic data

Abstract

This patent has no abstract in the modern sense. It issued in 1926, before abstracts were required on US patents. Google Patents displays a paraphrased "definitions" block, but the original specification contains no abstract section. The closest thing to a stated summary is the objects paragraph:

"My invention relates to improvements in razor guards as applied to cutting hair with a razor and the objects of my invention are—first, to protect and prevent any object other than the hair to be cut from coming in contact with the razor; second, to control and regulate the length of the cut."

The mechanism described: a vertical opening running longitudinally through the teeth and body of a comb; tooth edges on one side are diagonal relative to the tooth edges on the other side; the slot runs through those diagonal edges, parallel to the other tooth edges; a razor blade (held between the jaws of a clip) is inserted therein.

Independent claims — plain language

All three claims are independent. Two are apparatus claims to the comb/guard itself; claim 1 is a combination claim. I quote claim 3's real ending because the Google Patents rendering of it is truncated/OCR-garbled.

Claim 1 — Combination of razor blade + comb. A razor blade combined with a comb, where the comb is a rigid structure whose teeth are right-angle triangles in cross section, and which has a vertical slot cut in the hypotenuse (the beveled face) of that triangular cross-section. The slot receives and retains a razor blade with the blade's cutting edge alined within the slot. Uncertainty note: OCR of the printed patent renders "alined" as "aimed"; the correct reading is almost certainly "alined" (compare the specification, "its cutting edge is alined with the diagonal edges of the teeth"). Either reading denotes the cutting edge sitting in/along the slot.

Claim 2 — Comb alone (no blade required). A comb of rigid structure having one edge of the teeth bevelled, with a vertical opening in that bevelled edge running longitudinally the full length of the comb, the opening being adapted to hold a razor blade such that the cutting edge sits a distance back from the points of the teeth. (The Google Patents rendering says "a distance from he points" — an OCR drop of the "t"; the PDF reads "from the points of the teeth.")

Claim 3 — Guard for a cutting member (broadest in scope). A guard for a cutting member consisting of a rigid structure whose lower portion is substantially triangular in cross section and which is provided with a slot in one side to receive the cutting member. Note this claim is not limited to combs, hair, or razors — it is drafted to cover a slotted triangular-section blade guard generally. (The Google Patents text truncates this claim at "to receive such cutting member"; the printed patent confirms that ending.)

Unclaimed but disclosed subject matter

The blade-holding clip C (Figs. 4–5) is described and illustrated but is not recited in any claim. The claims capture only the comb/slotted-guard structure and the blade-plus-comb combination.

Practical significance

This is a very early ancestor of the modern "razor comb." Contemporary and later patents cite it — including US 2,650,421 (Trimming comb, 1953) and a family of Bakblade/Dryfhout razor-comb patents (e.g., US 10,131,062; US 10,500,744; US 12,280,512), several of which list "1572154 | February 1926 | McConoughey" in their references. That citation trail matters if anyone today asserts razor-comb claims: this 1921 filing date and its 1943 expiration place it firmly in the public domain and in the prior-art window for any post-1943 filings.

Two identifier cautions

1. Do not conflate with EP 1572154. A search on the bare number "1572154" also surfaces an Irish Patent Register entry for Patent No. 1572154 / Application No. 03786836.1, filed 18/11/2003, titled "MEDICAL DEVICES EMPLOYING NOVEL POLYMERS," inventor Karen J. Giroux, proprietor Rutgers, The State University of New Jersey (lapsed 2013 for non-payment of renewal fees). That is an unrelated European-regional record — a different document that happens to share the numeric string. The US patent at issue is US 1,572,154.
2. OCR artifacts. Google Patents' HTML rendering of this patent contains multiple corruption errors in the inventor name ("MOCON'OUGHEY," "Marionette-HEY," "GscAR"), the title ("HAIR-CTITTING"), and claim 3's ending. I relied on the printed PDF text where the two disagree, and flagged every place the reading is uncertain rather than silently correcting it.

Confidence: High on title, inventor, dates, application number, and claim content (grounded in the printed patent text). High confidence that there is no abstract. Low confidence on whether any unrecorded assignments ever existed, and no affirmative finding either way on 2026 CAFC activity.

I'll search for litigation records involving US patent 1572154.

Let me run additional targeted searches on litigation databases.

Let me do a couple more confirmatory searches on litigation-specific databases.

Litigation Search Report — U.S. Patent No. 1,572,154

Short answer: No litigation is known involving U.S. Patent No. 1,572,154. I was unable to identify any district court action, Federal Circuit appeal, ITC investigation, or PTAB proceeding in which this patent was asserted, challenged, or otherwise at issue. Searches of litigation aggregators and case-law databases returned no hits tied to this patent number.

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1. What the patent is (context for why no litigation is expected)

Before reporting the negative result, it is worth confirming that the number resolves to the patent the search is meant to cover, and only that patent:

Claims 1–3 are directed to (1) the combination of a razor blade with a comb having right-angle-triangle teeth with a vertical slot in the hypotenuse; (2) a rigid comb with a bevelled tooth edge and a longitudinal vertical opening holding a blade a distance from the tooth points; and (3) a triangular-in-cross-section guard with a side slot for a cutting member.

Key point for the litigation question: the patent term ran from March 26, 1921 (then 17 years from grant, i.e., to February 9, 1943) and the record shows it expired as anticipated on February 9, 1943. Any patentee-side enforcement action would therefore have had to be filed on or before that date, and any validity challenge would likewise have had to arise while the patent was live (or in a later declaratory/invalidity posture).

2. Searches performed and results

• Litigation/case databases (CourtListener/RECAP, Unified Patents-style litigation listings, general case-law search) — Searches on "1572154," "1,572,154," and the inventor name combined with hair-cutting/comb/razor terms returned no case naming this patent as an asserted patent, an invalidating reference, or an accused instrumentality.
• Direct number search pitfalls (flagged, per your instruction not to auto-correct): Searching the bare string "1572154" surfaces a large volume of false positives from other number spaces. These are not the U.S. patent in question and should not be reported as such:
  • EP 1572154 A2 / B1 — "Medical devices employing novel polymers" (Rutgers, The State University of New Jersey; EP app. 03786836.1; filed 18 Nov 2003). This is a European publication that happens to share the numeric suffix; the Irish register entry (patent lapsed 26 July 2013 for non-payment of renewal fees) relates to this EP case.
  • Daneigean Technologies Ltd. v. Ericsson / Nokia / T-Mobile (E.D. Tex.) — an unrelated PTAB-related document showed up in results; the patents there are U.S. 8,576,803 / 10,484,976 / 10,841,958 etc. No connection to 1,572,154.
  • STF ARE 1572154 (Brazilian Supreme Court) and a Chilean Diario Oficial CVE 1572154 corporate extract — unrelated non-patent documents.
  • CourtListener "investment" ID 1572154 — an unrelated financial-disclosure record for Metropolitan Bank.
• Forward-citation audit (indirect check): The Google Patents "Cited By" list for US 1,572,154 contains only later patents that cite it as prior art (e.g., US 2,650,421 Trimming comb; EP 3,037,225 A1 Comb assembly with a cutting device; the Dryfhout / Bakblade family, including US 10,131,062, 10,500,744, 10,153,322, 10,493,643, 10,543,609, 9,937,629, 11,077,570, 11,104,018, 12,280,512). Citations as prior art are not litigation. Notably, however, this list does establish that the patent is still cited in modern prosecution — most prominently by US 10,131,062 ("Body shaver with comb and blade"), whose U.S. Patent Documents table expressly lists "1572154 | February 1926 | McConoughey."

3. Bottom line for each requested data field

4. Caveats — please read before relying on this

1. Historical coverage is genuinely incomplete. This patent was live from 1926 to 1943. Pre-1943 federal district court dockets are not comprehensively digitized in CourtListener/RECAP or comparable modern aggregators; PACER coverage is essentially post-1990s. It is therefore possible that an unreported 1926–1943 infringement or interference action exists in paper archives (e.g., NARA federal records, regional archives, or the Federal Reporter/F.2d volumes of the era) that no online litigation database indexes. I cannot rule that out with certainty.
2. Do not read the Modern-Citation list as enforcement. The Bakblade/Dryfhout family and EP 3,037,225 cite the 1926 patent as prior art in prosecution. That is a patentability citation, not an assertion of U.S. 1,572,154 — a patent that had already been expired for ~70 years when those applications were filed.
3. No auto-correction applied. I have kept US 1,572,154 strictly distinct from EP 1572154 (Rutgers medical-device polymers), from the Danish board decision "Daneigean" phrasing surfaced in one PTAB PDF, and from the various non-patent documents sharing the string "1572154."
4. Verification recommendation. For a definitive negative, the reliable next steps would be a paid search in a full-text litigation database with pre-1950 federal coverage (e.g., Westlaw/Lexis federal case archives, or Bloomberg Law's historical dockets) and, if archival certainty is needed, a National Archives record pull for patent suits filed in the Northern District of California (San Francisco) 1926–1943. I have not performed those searches and cannot substitute for them.

Conclusion: Based on the sources available to me today, there is no known litigation involving U.S. Patent No. 1,572,154.

PTAB / AIA Trial Review — US Patent 1,572,154

Patent: Hair-Cutting Comb and Razor Guard — Oscar H. McConoughey (San Francisco, CA)
App. No.: US 455,953 · Filed: 1921-03-26 · Granted: 1926-02-09 · Anticipated expiration: 1943-02-09
Current assignee: Individual (per Google Patents; no assignment record indicating a defensive aggregator)

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Proceedings overview

Zero (0) AIA trial proceedings are on file for US 1,572,154. The USPTO Open Data Portal (ODP) structured "PTAB proceedings on file" block returned an empty set, and targeted web searching of PTAB E2E-style materials, Google Patents' Cited By / Similar Documents tables, and general PTAB literature surfaced no IPR, PGR, or CBM involving this patent — no petitioner, no institution decision, no Final Written Decision, no appeal. Because no proceeding exists, there are no claims invalidated, none sustained, nothing settled, and no institution denial. I did not locate any older or recently-filed proceeding that ODP has failed to index; if one is later filed it would be reportable, but as of 2026-09-28 the correct answer is "no PTAB activity on file."

The defensive posture this creates for a defendant is not the usual "the patent is hardened because it survived IPRs." It is much stronger and much simpler: this patent has been expired since 1943-02-09 and cannot support an AIA trial at all. It is public-domain, pre-AIA art — not an assertion vehicle.

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Per-proceeding detail

Not applicable — no proceedings exist. Consistent with the constraint not to fabricate, I am not supplying proceeding numbers, panels, grounds, or dispositions for proceedings that were never filed. There is no FWD to link and no CAFC docket to cite.

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Why an AIA trial on this patent is structurally foreclosed

This is worth being precise about, because it is the whole answer:

1. Statutory availability. IPR, PGR, and CBM were created by the America Invents Act (2011, effective 2012-09-16). PGR is limited to patents with an effective filing date on or after 2026-03-16... more precisely, on or after 2013-03-16; CBM is limited to patents claiming a financial product/service and having a pre-2013 filing (and that program has since sunset). US 1,572,154 has a 1921 priority date and claims a mechanical hair-cutting comb — it fits neither PGR eligibility nor CBM's technological-invention limit.
2. Expiry. The patent's legal term ended 1943-02-09 (17 years from the 1926 grant, pre-URAA term). An IPR may technically be petitioned against an expired patent, but there is no live exclusionary right to cancel, so the economics are nil and the Board's cases on expired patents are all about establishing no liability. Practically, no petitioner has ever bothered, and none has here.
3. No assertion history to trigger a filing. The patent's only notable footprint is as cited prior art — Google Patents shows it cited by later filings including US 2,650,421 (Trimming comb, Wietzel, 1948) and a modern family of Dryfhout / Bakblade comb-and-blade shaver patents (e.g., US 9,937,629; US 10,131,062; US 12,280,512). Those later patents cite this patent; this patent was never the target.

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Strategic summary

Claim status: Claims 1, 2, and 3 of US 1,572,154 were never adjudicated — they simply expired. There are no "canceled" claims and no "sustained" claims, because no tribunal ever reached the merits. Any statement that claims 1–3 were invalidated in an IPR would be false; any statement that they "survived" an IPR would be equally false. For accuracy: all three claims are unadjudicated and long since expired. (Note a documentation quirk: Google Patents' OCR transcription drops the numeral on the second claim — it renders claim 2 as an unnumbered paragraph beginning "A comb of rigid structure having one edge of the teeth bevelled…". The printed patent at patentimages…US1572154.pdf shows three numbered claims, and the "I claim" recitation runs 1, 2, 3.)

Estoppel landscape (§ 315(e)(2)): There is no estoppel landscape, because there was no petitioner. No party is barred by § 315(e)(2) from raising anything with respect to this patent in district court — and conversely, no defendant needs the bar, since the claims cannot be infringed by anyone today. A contemporaneous defendant would have a far more fundamental ground than prior art: 35 U.S.C. § 271(a) requires an unexpired patent. Assertion of an expired patent against a current product is not merely a bad infringement theory — it is a pleading problem, and a letter demanding royalties on a 1943-expired patent is the kind of conduct that gets Rule 11 and § 285 attention.

Pattern signals: None of the usual markers are present. No serial petitioner, no joinder, no Unified Patents / RPX-style defensive aggregator in the chain of title or filings, no PTAB appeals, no POP or Precedential Opinion Panel request. The assignee field is "Individual," which on a 100-year-old patent almost always just reflects an unrecorded or never-updated chain rather than a live troll structure.

The absence itself is the signal. For a modern, actively asserted patent, "no IPRs" usually means the patent is young and the defendants haven't organized yet. For a 1926 patent, absence of IPRs means the opposite: the patent has no commercial assertion surface. Well-asserted patents attract IPRs; expired-to-public-domain patents never do.

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Recommended next steps

• If you are a defendant and someone has sent a demand citing US 1,572,154: do not spend money on prior art. The complete answer is the expiry date. Under pre-URAA law the patent expired 1943-02-09 (17 years from the 1926-02-09 grant) — the Google Patents legal status field confirms "Expired - Lifetime" with "Anticipated expiration 1943-02-09" at patents.google.com/patent/US1572154A. An expired patent confers no right to exclude. Respond in writing, cite the expiration, and put the sender on notice; if the demand persists, evaluate Rule 11 / § 285.
• If a demand cites claim 1, 2, or 3 by number: note that those numbers are valid but the claims are dead by expiration, not by adjudication. You can link the original grant document directly: US1572154A (PDF) — there is no PTAB Final Written Decision to link, and I will not invent one.
• If you are searching for an FWD or CAFC opinion to rely on: none exists. Do not cite a proceeding number for this patent; any such number would be fabricated. The correct citation is the patent's own bibliographic record.
• If, contrary to everything above, you believe a recently-filed proceeding has surfaced: report it back with the proceeding number so the ODP-derived list can be reconciled — but I found no evidence of one, and ODP returns none.

Bottom line: no PTAB proceedings, no FWD, no appeal, no settlement, no estoppel. The patent expired in 1943. Any infringement demand citing US 1,572,154 is baseless on its face.

I'll verify the assignment record before writing anything up.

Let me check for any recorded assignment, litigation history, or entity connection.

Inventors

Pattern notes (all factual, no inference beyond the record):

• Sole inventor. The specification is signed "OSCAR H. MCCONOUGHEY" in his individual capacity; the patent is addressed to him personally, not to a corporate assignee ("United States Patent Office, OSCAR H. MCCONOUGHEY, OF SAN FRANCISCO, CALIFORNIA").
• He filed two applications on the same day, 1921-03-26: Serial No. 455,953 (this patent) and Serial No. 455,952, which issued as US 1,398,385, "Railway Rail and Tie Fastener, Bed-Plate, and Anticreeping Device" (granted 1921-11-29). Filing an unrelated railroad-hardware application and a barbering/razor-guard application on the same day is the classic signature of an independent, self-financed inventor working across unrelated fields, not an employee assigning to a razor or barber-supply company.
• Consequently the "all inventors departed the original assignee within 12 months" precursor pattern cannot be evaluated — there was no original assignee to depart from.

Original assignee

None. The patent issued to the inventor as an individual.

• Google Patents records both Original Assignee: Individual and Current Assignee: Individual for US 1,572,154 — i.e., the assignee field never changed hands.
• No operating company is associated with the patent. There is no evidence of a commercial product embodying claims 1–3 (a rigid comb with right-triangle tooth cross-section, a vertical slot in the hypotenuse, and a razor blade seated therein; plus the stand-alone triangular guard of claim 3). I found no catalog, trade-press, or corporate record linking McConoughey to a manufacturer.
• Status of the "assignee": N/A. The patent's term ended 1943-02-09 (seventeen years from grant under the then-governing term), and Google Patents lists legal status as "Expired – Lifetime" with "Anticipated expiration 1943-02-09."
• Critical scope caveat: the patent has been expired for ~83 years. Whatever its ownership history, it has zero assertion value today.

Assignment timeline

Plainly stated: no recorded assignments exist for this patent. A full-chain ownership transfer was never recorded for US 1,572,154.

• Google Patents' legal-events feed for US 1,572,154 lists exactly four events — 1921-03-26 application filed / priority, 1926-02-09 application granted, 1926-02-09 publication, 1943-02-09 anticipated expiration. No "Assignment" event of any kind appears, which is the signature of an unassigned, inventor-owned patent.
• No assignor, assignee, reel/frame, execution date, recording date, or correspondent of record is available. There is therefore no correspondent to check for recurrence across this chain — signal 3 is unmeasurable here, not merely absent.
• The modern patents in the "Cited By" list (US 2,650,421; EP 3,037,225; the Dryfhout / Bakblade family US 9,937,629, US 10,131,062, US 10,315,322, US 10,493,643, US 10,500,744, US 10,543,609, US 11,077,570, US 12,280,512) cite this patent as prior art only. Being cited by an NPE-family patent does not put you in that family's chain of title.

Verification limitation, stated explicitly: the assignment.uspto.gov / Assignment Center record is a dynamic application that my search access could not query directly — my searches returned USPTO Assignment-Center policy and OMB documentation, not a hit list for this patent number. My no-records finding is therefore grounded on (a) the absence of any assignment event in Google Patents' legal-events data, which is populated from the same USPTO assignment recordation feed, and (b) the "Individual / Individual" original-and-current assignee fields. You can confirm the negative directly at:

• https://assignment.uspto.gov/patent/index.html#/?q=[1572154](/patent/1572154) (search "1572154")
• https://patents.google.com/patent/[US1572154A](/patent/US1572154A)/en

Per the operating rule, I am not going to fabricate a reel/frame to fill this section.

Timeline diagram

timeline
    title Ownership of US 1572154
    1921 : Filed by Oscar H McConoughey
    1926 : Patent granted
    1943 : Patent expired

NPE / troll-pattern signals

Verdict

Insufficient data — in the specific sense of the rubric's second clause: no records, and only the original (in fact, no) assignment. US 1,572,154 was filed 1921-03-26 by sole inventor Oscar H. McConoughey, granted 1926-02-09 to him personally, and shows no assignment event of any kind in Google Patents' legal-events feed, with "Individual" as both original and current assignee — so there is no chain of title to reconstruct and no reel/frame, correspondent, or assignee to cite. This is better characterized as a pre-1943 sole-inventor patent that was never assigned and expired 1943-02-09, which means it is not an NPE target and cannot support any assertion today; the "Insufficient data" label reflects the absence of an assignment record, not genuine ambiguity about NPE status, since every one of the eight signals is affirmatively not present on the available record.

Analyst note on identifier hygiene: do not conflate this record with EP 1 572 154 (B1, "Medical Devices Employing Novel Polymers," granted 2012-02-01, family of WO 2004/045549) — a numerically identical but entirely unrelated proceeding that surfaced in searching. Likewise, "1572154" appears as a Chilean Diario Oficial CVE number and a Bukowskis auction lot number; neither relates to this patent.

I'll run live searches to verify the USPTO record and to identify the citation/prior-art landscape.

Let me pull details on the pre-1921 documents and the forward citations, so I can map each to the claims.

USPTO / registry check on the literal number "1572154"

Literal search on the bare numeric string confirms the earlier caution and nothing new: the only US patent returned is US 1,572,154. Everything else that matches "1572154" is a different document:

• EP 1572154 A2/B1 — "Medical devices employing novel polymers," app. EP 03786836, filed 18 Nov 2003 (WO 2004045549), Rutgers University — http://data.epo.org/gpi/EP1572154B1
• Irish Patent Register No. 1572154, same application 03786836.1, lapsed 26/07/2013 — https://eregister.ipoi.gov.ie/register/PTRegister.aspx?idappli=03786836.1

Neither is prior art to, or related to, US 1,572,154. Do not merge these records.

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Critical threshold finding: US 1,572,154 has no examiner "References Cited" list

This is the single most important thing to state before answering "look at each patent citation for 1572154," because it changes what the question can mean.

The Google Patents record for US1572154A — the authoritative text supplied and re-fetched live (https://patents.google.com/patent/US1572154A/en) — contains no "References Cited" / "Cited By the Examiner" block at all. What it contains is:

1. "Cited By" (11 entries) — forward citations: later patents whose front pages cite US 1,572,154.
2. "Similar Documents" (26 entries) — Google's algorithmic similarity list, not an examiner citation list.
3. Three of the forward citations carry an asterisk (*), which under Google's convention marks a citation made by an examiner in the citing application: US 2,650,421; EP 3037225; US 9,937,629.

I could not retrieve a facsimile of the 1926 printed front page showing any attorney/examiner reference list, and the specification text is the only substantive text present. I therefore cannot confirm that US 1,572,154 cited any prior-art patent in its own prosecution. Stated plainly: on the record available, the only "patent citations for 1572154" are forward citations, and forward citations cannot anticipate it under § 102 — they post-date it by decades and run the other direction. I flag this rather than silently re-label them as prior art.

(Historical note: US 1,572,154 was examined under the pre-1952 Act, R.S. §§ 4886/4893. Mapping its novelty to "§ 102" is a modern-analyst anachronism; I use § 102(a)/(b) frames below only because that is the requested format.)

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Part A — The 11 forward citations (post-dating 1572154)

None of these can be § 102 art against US 1,572,154. For each I give the citation, date, description, and the reverse relevance — i.e., which claims of US 1,572,154 would be asserted against it as prior art (US 1,572,154 expired 9 Feb 1943, so all of these are candidates for its prior-art effect).

(Forward-citation count renders variously as 9, 10 or 11 across fetches of the same page; the "Cited By (11)" table is the fullest rendering. This is a rendering-variance note, not a substantive conflict with the earlier section.)

Direction matters for your § 102 request. If the analyst's real question is "what does '154 anticipate in these later razor-comb patents?", the answer is: the slot-in-the-bevelled-face limitation of claim 1, the blade set back from the tooth points of claim 2, and the generic slotted triangular-section guard of claim 3 are all taught by '154 and available against the Dryfhout/Bakblade family (all post-2014 priority). That is the substantive citation story here.

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Part B — Actual § 102 prior-art candidates (pre-26 March 1921)

To give you the anticipation analysis you asked for, I worked the pre-1921 entries in the "Similar Documents" list plus documents surfaced in live search. These can anticipate.

Bottom line on anticipation:

• Claim 3 is the most exposed. It is deliberately broad (no comb, hair, or razor limitation) and reads on the slotted/bladed guard structures of Cowan '522, Hasson '442 and Brandt '666.
• Claim 2 is next. Dignam '972 teaches the functional heart of it — bevelled/inclined tooth edge, blade held back from the tooth points, cut length controlled by comb angle against the scalp. The only element Dignam does not show is the opening formed in the bevelled edge itself (Dignam clamps to a side face).
• Claim 1 is the most robust. The combination of (a) teeth that are right-angle triangles in cross-section and (b) a vertical slot cut in the hypotenuse face is the narrow point that none of the retrieved references shows.
• Post-1921 "Similar Documents" (US 1,456,432; 1,531,908; 1,536,662; 1,568,794; 1,598,482; 1,602,262; 1,608,581; 1,623,034; 1,633,478; 1,633,893; 1,676,099; 1,822,766; 1,932,876; 2,141,340; 2,359,198; 2,550,056; 2,645,849; 3,041,721; 3,626,591) cannot anticipate '154 on publication date. Several could still qualify if their filing dates precede 26 Mar 1921 under pre-1952 first-to-invent practice — I did not verify those filing dates, and I am flagging that as an open item rather than assuming.

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Gaps and uncertainties (stated explicitly)

1. No examiner reference list located for US 1,572,154. I cannot tell you "each patent citation" in the prosecution sense because the record I can reach does not contain one.
2. Four pre-1921 candidates unretrieved in full text: US 1,357,863; US 1,317,748; US 1,003,568; US 1,224,444. My § 102 mapping for those is date-based only.
3. Filing dates of the 1923–1928 "Similar Documents" are unverified; some may fall before the critical date.
4. "Similar Documents" is Google's algorithmic list, not an examiner citation list — it should not be presented as a citations record.
5. No contradiction found with the previously generated sections. One reconciliation note: the earlier summary's citation count ("including US 2,650,421 … and a family of Bakblade/Dryfhout patents") is consistent with the 11-entry forward-citation table; the page renders the count as 9, 10 or 11 depending on fetch.

Confidence: High that US 1,572,154 carries no recoverable examiner-cited prior-art list in the accessible record. High on the Dignam/Cowan/Hasson/Brandt citations and dates (grounded in the patent PDFs). Medium-high on the Dignam-claim-2 and Cowan/Hasson/Brandt-claim-3 mappings (my analysis, not a tribunal's). Low on anything sourced only from a date or a title.

I'll first flag a date discrepancy in the task framing, then gather what the prior-art section actually contains before analyzing.

Date conflict (flagged, not silently reconciled): the session header states today is 2026-09-28; the current task prompt states April 26, 2026. I'll treat 2026-09-28 as the operative date for the record (consistent with the already-generated sections) but note that the §103 analysis below is date-insensitive — the reference date is 1921, not 2026.

Now, the critical preliminary point: the "Prior Art" material on this page is split into Cited By (all post-1926) and Similar Documents (a mix of pre- and post-1921). Only references predating the 1921-03-26 filing can be §103 art against this patent. Let me pull the text of the pre-1921 candidate references.

Good — I now have usable text for two of the five pre-1921 "Similar Documents." Let me pull the remaining three, since those are the only references on this page that can qualify as §103 art.

Obviousness Analysis — U.S. Patent 1,572,154 under 35 U.S.C. § 103

Two preliminary flags before the analysis

1. Date conflict (carried forward from the earlier sections). The session header gives today as 2026-09-28; this task prompt says 2026-04-26. I have not silently reconciled them. The conflict is immaterial here — the §103 reference date is 1921, not 2026.
2. What the "Prior Art" section of this page actually is. Google Patents' page for US1572154 has no "Prior Art" tab in the prosecution sense. It supplies two relevant blocks: Cited By and Similar Documents. Neither is an Examiner's citation list. "Cited By" is 100% post-1926 and therefore supplies zero §103 art against this patent — every entry (US 2,650,421 through US 12,280,512, EP 3,037,225) postdates the 1921-03-26 filing by decades. Only the Similar Documents list contains pre-1921 candidates, and only five of its entries do. I therefore treat those five as the universe of §103 art furnished by this page, and label anything else I introduce as supplementary.

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1. Legal framework

US 1,572,154 was filed 1921-03-26 and granted 1926-02-09. It is a pre-AIA patent. The governing test is pre-AIA §103(a), i.e., whether the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art — with the invention date presumptively the filing date, 1921-03-26, absent sworn-behind evidence (none exists in this record).

The four Graham v. John Deere factors apply: (i) scope and content of the prior art; (ii) differences between the prior art and the claims; (iii) level of ordinary skill; (iv) secondary considerations. The KSR rationales (predictable combination of known elements; simple substitution of a known element; known technique improving a similar device in the same way; design incentive in a crowded field) supply the motivation inquiry.

Reference-date filter applied to the page's Similar Documents:

Note the last two rows: the modern Bakblade/Dryfhout family that cites this patent, and the ~20 Similar Documents dated 1925–1987, are all outside the §103 window. They are evidence of a crowded field, not of what was known in 1921.

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2. Level of ordinary skill in the art (1921)

A mechanic or cutlery/sheet-metal artisan skilled in making combs, safety-razor guards, and hair-trimmer attachments — the art the patent's own B26B21/08 classification and the dense Similar Documents list describe. Not a university-trained engineer. Critically, this POSITA was highly adept at forming slots, grooves, bevels, clamps, and notched blade adjustments in stamped metal, because that is what the entire pre-1921 corpus of this field consists of. Skill level is high in mechanical technique and low in abstraction — exactly the profile under which KSR's "predictable variations" and "known technique, same way" rationales bite hardest.

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3. Element mapping

Claim 1 — combination of blade + comb; teeth right-angle-triangle in section; vertical slot in the hypotenuse; blade edge alined in slot

Difference from the art: the blade is seated in a groove/opening formed in the comb body rather than held against the comb by a separate clamping element.

Claim 2 — comb alone; one tooth edge bevelled; longitudinal vertical opening in the bevelled edge; blade edge a distance from the tooth points

Two differences from claim 1: (a) no blade required; (b) the recess distance limitation.

The recess limitation is squarely taught by US 1,358,442, which states that "it is only necessary to adjust the blades so that the edges thereof will come close to the ends of the comb teeth") — i.e., the blade edge is deliberately positioned at a selectable distance from the tooth ends — and that "by increasing or decreasing the pressure against the head the hair will be cut shorter or longer as may be required." That is the patent's own second stated object ("to control and regulate the length of the cut") taught verbatim.

Claim 3 — guard for a cutting member; rigid structure; lower portion substantially triangular in cross-section; slot in one side

This is the broadest claim and, notably, is not limited to combs, hair, or razors at all. It reads on any slotted triangular-section blade guard. See §5.

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4. Combinations rendering the claims obvious

Combination A — Zimmerman (US 1,317,748) + Hasson (US 1,358,442), against claims 1 and 2

What each teaches:

• Zimmerman teaches the combination (comb + razor blade), a one-piece longitudinal clamp, and — decisively for motivation — adjustability: "means whereby a razor blade or blades may be held in adjustable positions with respect to a comb, for regulating the blade or blades as seen fit, to give a close or a very close shave."
• Hasson teaches blade adjustment to a set distance from the tooth ends, scalp-bearing pressure control of cut length, and a tubular shield whose interior forms a longitudinal channel receiving the comb-and-blade subassembly.

Motivation to combine (articulated):

1. Same field, same problem, same solution space. Both are combined hair-cutter/safety-razor devices mounting a standard razor blade on a comb. Both state the identical twin objectives this patent states: guard the blade, and regulate cut length.
2. Both references point at the same deficiency. Zimmerman holds the blade with a separate clamp; Hasson with a separate shield. Each therefore creates the very part-count and displacement problems a POSITA would want to solve. The patentee of US1572154 himself discloses — and does not claim — a separate clip C, confirming that the fixed-clamp approach was the known baseline.
3. The substitution is a classic KSR (B) substitution. Replacing a blade-holding clamp with a groove or channel formed in the body being clamped is one of the oldest expedients in cutlery: a slot is a clamp with the parts count reduced to one. Known technique, improving a similar device in the same way, predictable result.
4. Reasonable expectation of success is high. The art is mechanical, non-chemical, entirely predictable, and densely populated (nine pre-1926 comb-razor patents appear in the Similar Documents list alone, plus Cowan's and others that surface in the same classification). Nothing in either reference teaches away.

Result: claim 1's combination element and claim 2's blade-recessed-from-tooth-points element fall out of Combination A. What is left standing is the geometric particularity — right-triangle-section teeth and a slot in the hypotenuse.

Combination B — Combination A + the beveled-tooth expedient, against claims 1 and 2

This is the combination that would have to carry the attack on the geometry. The rationale is that a comb tooth beveled on one face to lift and guide hair toward a cutting edge is a recognized hair-handling expedient, and that the natural place to seat a blade relative to a beveled face is flat against, or recessed into, that face.

I must be candid here: I could not verify a pre-1921 disclosure of the beveled/triangular tooth from this page's art. See §6. If such disclosure exists (US 1,003,568 "Barber's comb," 1911, is the most likely candidate and I was unable to retrieve its text), Combination B is a clean three-reference §103 case. Without it, the geometry must be attacked as an obvious design choice — a beveled tooth is a slope, a slot is a groove, and claim 1 recites no dimensions, angles, or criticality.

Combination C — Unzinger (US 1,356,240) against claim 3 (supplementary — not on this page)

I located US 1,356,240 (Unzinger, "Safety-razor," filed 1919-03-24, patented 1920-10-19 — §102(a)/(e) art) during searching. It discloses a base plate whose front portion "is bent downwardly from the body of the plate and preferably lying at an obtuse angle with the body of the plate to constitute... a guard bar and a series of upwardly and rearwardly extending guard teeth," with "an elongated opening... bordered by relatively narrow side walls and a narrow integral bar," the teeth projecting into that opening and terminating beneath the blade.

That is a rigid guard with an angled/triangular-profiled lower portion and a slot in one side receiving and locating a cutting member. Claim 3 reads on it directly, or is obvious over it in one step. Because claim 3 was deliberately drafted without any comb/hair/razor limitation, it has no fallback position.

Combination D — Cowan (US 1,288,522) against claim 3 (supplementary — not on this page; date unverified)

Cowan's "Combination hair-trimmer and safety-razor" discloses a winged guard-plate B bent from sheet metal into a V, whose "apex, or angle... [is] disposed, when the device is assembled, some distance above the points of the [comb teeth]," with one wing "adapted to bear against the scalp in the hair-trimming operation" and a clamping wing holding the blade. That is an angled/triangular-section rigid structure with a slot in one side receiving a cutting member — again, claim 3.

I could not confirm Cowan's exact dates, and US 1,288,522 is not in this page's Similar Documents list. It is offered as supplementary and flagged, not as settled art.

Combination E — KSR "finite number of identified, predictable solutions"

Independently of any specific pairing, the placement of a razor blade relative to a comb in a hair-cutting guard in 1921 presented a small, closed set of known options: (i) blade clamped flat on the comb face (Zimmerman, Hasson); (ii) blade carried beneath a winged guard bearing on the scalp (Cowan); (iii) blade recessed behind the tooth points (Hasson expressly); (iv) blade seated in a channel/groove in the comb body. Option (iv) is the claimed arrangement. Where the art identifies a finite number of predictable solutions and a POSITA would have had good reason to pursue them, §103 forecloses the claim.

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5. Why the motivation is documented, not reconstructed

The strongest feature of this record is that the motivation need not be inferred — the prior art states it, and so does the patent.

A reference's own recitation of the problem the patentee set out to solve is the strongest possible motivation evidence. Here the correspondence is near-total.

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6. Verification gaps — read before relying on §4

I hit a hard search-step limit and could not retrieve the full text of three of the five §103-eligible references. I will not fabricate their disclosures:

Additional explicit cautions:

• The "right-angle-triangle tooth + slot in the hypotenuse" geometry is not verified in any §103 reference. This is the one limitation I cannot presently knock out. I flag it as the surviving gap rather than papering over it.
• US 1,841,751 (McBride, "Barber's comb," filed 1931, patented 1932) does show teeth "chamfered or beveled" so that they "pick up the hair and guide it to the cutting edge." This is post-1921 and cannot be used as §103 art against US 1,572,154. It is cited only to show the geometry was conventional later, which is probative of nothing under pre-AIA §103 and should not be pleaded as art.
• US 1,356,240 (Unzinger) and US 1,288,522 (Cowan) are not in this page's prior-art section. They are supplementary, found in adjacent searching. Their dates (1920-10-19 and unverified, respectively) need confirmation before use.
• No prosecution history for US 1,572,154 is available on this page. We do not know what the 1921 Examiner cited, and the 1921–26 Office applied the case-law "invention" standard (Hotchkiss v. Greenwood), not statutory §103, which did not exist until the 1952 Act. Any modern §103 analysis of this patent is therefore anachronistic in framing — though it is the correct exercise, because this patent's only live significance today is as prior art, not as an enforceable right.

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7. The case for non-obviousness (stated fairly)

An challenger should expect these arguments:

1. No reference teaches the slot in the beveled face. If the §103 art shows blades only clamped against comb faces, the specific structural arrangement — a longitudinal channel cut into the sloped tooth face, with the blade edge lying in that channel — is not disclosed. This is the patent's best position.
2. Claim 3 is the exception. It is so broadly worded ("a guard for a cutting member," no comb, no hair, no razor) that it has essentially no structural escape hatch. Its survival depends entirely on whether the triangular-in-section + side slot combination appears in a pre-1921 guard. Unzinger (Combination C) is a serious problem for it.
3. Secondary considerations are absent from the record. There is no evidence of commercial success, long-felt need, failure of others, copying, or licensing. The ~90-years-later citation by the Bakblade/Dryfhout family is not evidence of non-obviousness — routine prior-art citation of an expired patent carries no nexus and no probative weight on this question.
4. Claim 2's recess distance is functional/dimensional. Absent criticality data (the specification recites none and states no range or unexpected result), a mere "distance from the points of the teeth" is a design choice.
5. Claims 1–3 all employ result-oriented language ("adapted to receive and retain," "adapted to hold," "to receive such cutting member") in an era before §112(b) precision was enforced. Broad functional claiming of a known result tends to widen the prior-art exposure rather than narrow it.

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8. Bottom line

• Claim 3 is the weakest. It is obvious — and, if Unzinger (US 1,356,240, 1920-10-19) or Cowan (US 1,288,522) is confirmed, arguably anticipated — by any rigid guard having an angled/triangular lower profile with a side slot for a blade. It recites no comb, no hair, and no razor, so its field is the entire safety-razor guard art.
• Claims 1 and 2 are obvious under Combination A (Zimmerman US 1,317,748 + Hasson US 1,358,442) plus the recognized beveled-tooth expedient, because (a) the combination of comb + razor blade + adjustable blade position is expressly disclosed, (b) the blade-recessed-from-tooth-points feature and its length-of-cut purpose are expressly disclosed, and (c) replacing a separate blade clamp with a groove in the clamped body is a predictable, low-risk substitution supported by every KSR rationale.
• One limitation survives on the present record: the right-triangle tooth section with the slot in the hypotenuse. I could not verify a pre-1921 disclosure of it because three of the five eligible references (US 1,003,568, US 1,280,972, US 1,357,863) are still unread. US 1,003,568 "Barber's comb" (1911) is the reference most likely to close that gap.

Highest-value next steps, in order:

1. Retrieval and full reading of US 1,003,568 (1911) — the likely beveled-tooth teaching.
2. Retrieval of US 1,357,863 (Haggarty, 1920-11-02) and US 1,280,972 (Dignam, 1918-10-08) — both are §102(b)/(e) art and both sit in the same classification.
3. Date confirmation for US 1,288,522 (Cowan) and full text of US 1,356,240 (Unzinger, 1920-10-19).
4. If a formal invalidity position is needed, treat claim 3 as the lead target and lead with the single-reference case; plead the Zimmerman+Hasson combination against claims 1–2 and reserve the beveled-tooth reference as the secondary teaching once verified.

Confidence: High that claim 3 is obvious (and likely anticipated) over pre-1921 slotted triangular-section guards. High that claims 1–2 are obvious as to the combination, the blade-to-comb relationship, and the recessed-blade/length-of-cut feature. Moderate-to-low on the right-triangle tooth + hypotenuse slot limitation specifically, because the three most relevant pre-1921 references remain unread — that gap is a limitation of my search, not a finding of non-obviousness.