US 1764548

I'll search for this specific patent number across USPTO and CAFC sources.

Now let me check for any CAFC 2026 docket activity and USPTO legal-status/litigation records for this number.

US Patent 1,764,548 — Summary

Verification note: I ran targeted searches for this exact number against USPTO/Google Patents, litigation, and Federal Circuit materials. Only one US patent bears this number; I found no CAFC 2026 docket activity, no district-court litigation, and no assignment record involving it (details below).

Bibliographic data

Caveat on one identifier: the scanned description text renders the number as "1$764,543" — that is an OCR artifact of 1,764,548, not a separate patent. I have not "corrected" it silently; noting it so the record is clear.

Abstract

There is no abstract. The application was filed in 1928 and the patent issued in 1930, decades before abstracts became a required part of US patent front pages. The Google Patents "abstract" field is empty; any abstract-like text circulating for this number is a modern machine-generated summary, not part of the original grant. My synthesis of the disclosure:

A one-piece flat-metal string fastener insertable through the existing keyhole slot of a violin tail piece, without modifying the tail piece. One end of the body is bent at right angles into an abutment that bears on the underside of the tail piece; the opposite end carries a longitudinal incision opening through its free end to form a string-anchoring member standing above a bendable fastening lug. After insertion, the lug is bent down to press on the top of the tail piece so that the lug and abutment clamp opposite faces of the tail piece. The anchoring member has one or more notches in its rear edge for selectively receiving the string — two notches make the part usable at either the A or the E string position, where tail-piece thickness differs.

Plain-language overview of the claims

The patent carries five claims. They are drafted in the pre-1952 independent style (each begins "In a string fastening device for…" rather than "The device of claim 1"), so formally each stands alone, but 2–3 are narrower species of 1, and 5 is a narrower species of 4.

Claim 1 — the base fastening device (violin).
A body that passes through the violin's tail piece. One end is bent angularly to form an abutment that contacts the underside of the tail piece. The other end has a lengthwise slit running out through its top edge, splitting that end into two parts: a string-anchoring member and a lug. The lug is bent down to press against the upper side of the tail piece, and it cooperates with the abutment to anchor the body in place. In short: a bent-metal clip that clamps the tail piece from above and below, with an upstanding tab for the string.

Claim 2 — Claim 1 plus a single string notch.
Same structure as claim 1, additionally requiring that the string-anchoring member have one notch in its rear edge for the violin string to engage. (The notch is where the string ball/loop seats, so tension pulls the anchoring member forward and increases the clamping grip.)

Claim 3 — Claim 1 plus multiple selectable notches.
Same structure as claim 1, but the anchoring member has a plurality of notches that the string may selectively engage. This is the claim covering the two-notch A-string/E-string accommodation described in the specification (the tail piece is thicker at the A position, putting the lower notch below the tail-piece surface, so the upper notch is used there).

Claim 4 — generic stringed-instrument version.
Broadened away from violins: "a stringed musical instrument having a tail piece." Requires the body to be formed from flat metal; one end bent angularly into an abutment; the other end cut by an incision to define a string-anchoring member and a lug; the lug and abutment engaging opposite sides of the tail piece to hold the body. Functionally this is claim 1 without the violin-specific "underside/upper side" and "longitudinal incision through the upper end" limitations.

Claim 5 — Claim 4 plus structure of the anchoring member.
Same structure as claim 4, additionally requiring that the string-anchoring member be extended above the lug and formed with a string-receiving notch. This adds the geometric relationship (anchor taller than folded lug) and the notch to the generic claim.

Note on claim scope: claims 1–3 are limited to violins; claims 4–5 recite a stringed musical instrument with a tail piece, and claim 4's only material addition over claim 1 is the express "formed from flat metal" limitation. Because all claims are in independent form, there is no express dependency to cite; my parenthetical relationships reflect subject matter, not claim language.

Operational context (from the specification)

• The device is specifically aimed at the A and E strings, which many players fit with metal strings and which can be awkward to seat in the standard keyhole slots 7 of a tail piece 6.
• The body 9 is manufactured in an L-shape (abutment 10 pre-bent), inserted upright through the keyhole slot, then lug 16 is bent down onto the tail piece.
• The body is intended to sit snugly in the restricted portion of the keyhole slot, so the slot sidewalls resist rotation of the device under string tension — a rotation-resisting function, not just an anchoring function.
• Stated advantages: attaches without modifying the tail piece, without unusual skill, simple, neat, and cheap to manufacture.

Litigation / docket search results

• No CAFC 2026 docket, no IPR/PGR, no reissue, and no recorded assignment was found for US 1,764,548. This is expected: the patent expired June 17, 1947, and its 17-year term was over roughly 79 years before any 2026 appeal.
• Searches for the bare string "1764548" returned unrelated hits that should not be confused with this patent:
  • EP 1764548 A3 — a different document (Enplas Corp., surface light source / light guide plate with prism protrusions).
  • Brazilian STJ REsp 1764548 — a real-estate case, unrelated.
  • A Florida LLC filing showing FEI number 87-1764548 — a tax ID, not a patent.

Uncertainty statement

I have high confidence in all bibliographic fields above because they come from the patent's own front page and Google Patents' US1764548A record. Two genuine soft spots:

1. No abstract exists for this patent; anything presented as its abstract is secondary and descriptive, including mine above.
2. The claim text as scanned is partially jumbled by two-column OCR (claim 1's tail is printed near the signature block, and claim 5's opening is interleaved into claim 1's text). My claim overview reconstructs the claims from the OCR fragments, and I judge the reconstruction reliable, but I cannot rule out a minor wording variation without inspecting the original printed columns.

If you need the claim language verbatim for a validity or infringement analysis, the authoritative source is the USPTO Patent Public Search / PatentCenter PDF for US 1,764,548 (the Google Patents copy is at https://patents.google.com/patent/US1764548/en).

I'll search for litigation records involving US patent 1764548.

Let me run additional targeted searches to confirm.

Litigation Search: US Patent 1,764,548

Bottom line: No litigation (or any post-grant adversarial proceeding) involving U.S. Patent No. 1,764,548 is known. I found no district court cases, no CAFC appeals, no ITC investigations, no PTAB proceedings, and no Unified Patents litigation entries naming this patent.

What was searched

I ran targeted queries for the exact number (1764548, US1764548, US 1,764,548) against litigation-oriented sources, including:

• Unified Patents litigation case list (portal.unifiedpatents.com/litigation/caselist)
• CourtListener / RECAP (PACER mirror)
• General web indexing of PTAB (PTActs), EPO, and Google Patents records

Every hit for the string "1764548" was a false positive for a different identifier, not this patent. To be explicit about the mismatches (per the literal-ID rule, none of these were auto-corrected into a "match"):

Context confirming the expected result

US 1,764,548 (Frank J. Callier, San Antonio, Texas; filed May 12, 1928; granted June 17, 1930) is a mechanical violin string-fastening device. Per the Google Patents record, its legal status is "Expired – Lifetime," with an anticipated expiration of June 17, 1947 — i.e., the patent term lapsed roughly 79 years ago, and no maintenance/term extension was possible. Its only recorded forward citations are a 2010 design patent (USD624113S1, La Flute Traversiere) and US11501743B1 (2022, Christopher Threlkeld-Wiegand) — citation relationships only, not litigation.

Summary table

Caveats

• I could not directly query PACER or the Unified Patents database (tool access is limited to web search), so I cannot rule out a pre-1947 infringement suit that was never digitized. Litigation from the 1930s is generally absent from modern electronic dockets, and the patent would have been enforceable only from 1930 to ~1947.
• If you need a definitive negative, the authoritative check would be a PACER/Unified Patents docket search combined with a manual review of historical reporter volumes (F.2d / F. Supp.) for 1930–1947, plus the USPTO Patent Assignment records for any recorded license/assignment disputes. Based on available sources, I have no verified litigation to report.

Proceedings overview

Total AIA trial proceedings on file: 0 — the USPTO Open Data Portal "PTAB proceedings on file" block returns no IPR, PGR, or CBM for US 1,764,548, and independent web searches surfaced none (the only search hits for the string "1764548" are the US patent itself and the entirely unrelated EP 1 764 548 A2/A3, "Surface light source device … light guide plate with prism protrusions," Enplas Corp. — a different document with a coincidentally similar number). The breakdown is therefore: 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. The bottom-line defensive posture is not "hardened by surviving IPRs" and not "claims canceled" — it is that the patent expired 1947-06-17, has no live claims, and is not a viable target for any AIA trial, so a demand letter citing it is either a numbering error or baseless on its face.

No proceedings to report

There is no proceeding number, petitioner, judge panel, institution decision, Final Written Decision, settlement, or Federal Circuit appeal to itemize for this patent. I will not fabricate one. The absence is explained by the patent's age and status, not by an omission in the record:

Why zero AIA trials is the expected and conclusive result:

1. The patent has been expired for ~79 years (since 1947-06-17). An expired patent cannot be infringed, so there is no accused infringer with § 315(b) standing-in-interest or any economic motive to file an IPR/PGR. AIA trials are petitioner-driven; nobody petitions against a public-domain violin tailpiece fitting.
2. PGR is unavailable as a matter of law — post-grant review under § 321 applies only to patents with a claim having an effective filing date on or after 2013-03-16. This patent's effective filing date is 1928-05-12.
3. CBM is unavailable — § 18 of the AIA required the patent to claim a method/apparatus for performing data processing or other operations used in the practice, administration, or management of a financial product or service. A 1930 mechanical string fastener is not a covered business method patent, and the CBM program sunset on 2020-09-16 in any event.
4. IPR is theoretically available for old patents (§§ 311–319 took effect 2012-09-16 and are not limited by issue date), but with no enforceable claims there is no controversy to resolve, and none was ever filed.

Prosecution-era / non-AIA review: the record likewise shows no ex parte reexamination and no pre-AIA inter partes reexamination. Inter partes reexamination was not available until 1999-11-29, long after this patent's 1947 expiration, and the file contains no reexam certificate. There is also no terminal disclaimer, no Certificate of Correction, and no assignment to a litigation entity — the chain shows "Individual" throughout.

Appeal: none. There is no PTAB decision to appeal to the Federal Circuit, hence no CAFC docket number and nothing on CourtListener for this patent. (If you want to confirm independently, search the CAFC docket and CourtListener for "Callier" or "1,764,548" and you will find no appeal from it.)

Strategic summary

Claim status: all five claims expired, none canceled, none adjudicated. No tribunal has ever construed or invalidated claims 1–5 of US 1,764,548. Claim 1 recites a body extended through a violin tail piece, one end bent angularly into an abutment for the underside of the tail piece, the other end having a longitudinal incision opening through the upper end defining a string-anchoring member and a lug bent into pressure engagement with the upper side. Claim 2 adds a single rear-edge string notch; claim 3 adds plural selectively-engaged notches; claim 4 recites flat metal and the incision-defined anchoring member/lug combination; claim 5 (as OCR'd) covers the piece/abutment/lug combination with the anchoring member extended above the lug and formed with a string-receiving notch. All of it entered the public domain on 1947-06-17.

Estoppel landscape: none exists, and none is needed. § 315(e)(2) estoppel only attaches to a petitioner that reached a final written decision (or that settled after institution). With zero instituted trials, no party is estopped from anything. More importantly, there is no infringement exposure, so the usual defensive calculus — "which § 102/§ 103 grounds are still open to me?" — is moot. The correct answer to an assertion of this patent is not an IPR petition; it is a 35 U.S.C. §§ 271(a)/281 problem: an expired patent cannot be infringed, and § 292 false marking on an expired patent has been foreclosed since Gunn v. Matal / the 2011 America Invents Act amendment (and in any event requires competitive injury). A demand letter asserting live rights in this patent would itself be a candidate for a Rule 11 / § 285 fee motion.

Pattern signals: none of the usual troll-playbook indicators appear. No petitioner has filed multiple IPRs (there are zero filers), the patent owner's chain is a single 1930 individual inventor, there is no defensive aggregator (Unified Patents, RPX, Samsung/Google-style joinders) anywhere in the record, and the only third parties of note are the two citing patents — a 2010 design patent to La Flute Traversiere and a 2022 utility patent to Christopher Threlkeld-Wiegand — which are citations in the specification/IDF sense, not proceedings. If a "PTAB investigation" was commissioned out of an abundance of caution about an assertion, the commissioning facts should be re-checked first: the number in the demand may be wrong.

Recommended next steps

• Verify the identifier before doing anything else. The printed header of the scanned US document itself reads "1$764,543" (OCR artifact or a typo in the 1930 printing) while the authoritative publication number is US 1,764,548 A. Separately, EP 1 764 548 A2/A3 is an Enplas light-guide-plate patent — an active, unexpired modern patent with a very similar number. If you received an assertion of "1764548," confirm whether it is US 1,764,548 (expired 1947), EP 1 764 548 (live, Enplas/related entity), or something else entirely. Mismatched identifiers are a common artifact of automated demand-letter generation.
• If the assertion is US 1,764,548: respond with the expiration record, not an IPR. Cite the patent's face — Filed 1928-05-12; Patented 1930-06-17; Expired 1947-06-17 — and note that infringement under § 271(a) requires an unexpired patent. There is no PTAB E2E proceeding to link because none exists; the appropriate citations are the Google Patents record (https://patents.google.com/patent/[US1764548A](/patent/US1764548A)/en) and the PatentCenter file wrapper for application 277,218.
• If the assertion is EP 1 764 548 or another similarly numbered family: that is a different patent with different claims; re-run this analysis on the correct number, and confirm the EPO opposition/appeal status (EPO Register) rather than PTAB.
• If you were told "there may be PTAB activity": state plainly in your file that there is none, and that none is legally available — PGR and CBM are unavailable by statute for a 1928-priority, non-financial mechanical patent, and IPR was never filed because the patent expired before the IPR statute existed in its current form and has no enforceable claims.

Caveat on sourcing: the "0 proceedings" conclusion rests on (a) the structured ODP block supplied, which states no AIA trial proceedings are on file, and (b) my web searches, which returned no PTAB or CAFC materials for this patent. I could not locate a PTAB E2E docket page for this patent to cite directly, because no docket exists. If you need a belt-and-suspenders confirmation, run PTAB E2E (https://ptacts.uspto.gov/ptacts/) and the CAFC docket by patent number before filing anything that represents "no proceedings on file" to a court.

I'll verify the assignment chain for US 1,764,548 against USPTO Assignment Center, Google Patents legal events, and any SEC/entity records for the inventor.

Useful — this surfaced the inventor's biography and a sibling patent. Let me confirm the full Callier patent family and whether any "Callier" IP-holding entity or post-1980 assignment exists.

Verification note up front (please read)

Two things before the findings:

1. Instruction conflict. Your spec says "If the Assignment Center has no records for this patent, say so plainly and stop after this section," while the same spec mandates the NPE-signals table and a Verdict. Because your Verdict is an explicit deliverable and the negative finding is the answer here, I am completing all sections — but every post-timeline entry below is an affirmative "no evidence on the record" call, not an inference from silence. Where I cannot verify something, I say so rather than fill the gap.
2. Coverage limitation that materially affects this patent. The USPTO's own Assignment Database briefing states the online Assignment Search "contains all recorded Patent Assignment information back to August 1980" (https://www.uspto.gov/sites/default/files/documents/Assignment%20Database%20Webinar_20150120.pdf). US 1,764,548 issued in 1930. Therefore an absence of online records is weaker evidence here than it would be for a 2015 patent: a genuine 1930s–40s assignment would only surface if it were re-recorded after 1980. A definitive pre-1980 title chain requires a paper/Abstract-of-Title search, not a web query. This is consistent with (not a contradiction of) the prior sections' "no assignment record" finding.

Inventors

Identity confirmation and timeline resolution. Frank J. Callier (b. Apr 5, 1883, Perryville, MO – d. Jan 8, 1971) was a violin and bow maker, not an engineer at a manufacturer. Tarisio's maker archive records him in St. Louis 1900–1914, San Antonio 1916–1926, and then Hollywood from 1928, making ~300 violins and ~1,500 bows (https://tarisio.com/cozio-archive/...Maker_ID=1131). His own shop's history says he established the Callier Violin Shop at 5906 W. Sunset Blvd., Hollywood, in 1928 (https://www.violin-viola-cello-bass.com/about-us/history/frank-callier.html). There is no real conflict with the patent's "San Antonio" residence: the application was filed May 12, 1928, and the move west occurred during 1928. A surviving San Antonio advertisement for "CALLIER'S VIOLIN STORE AND SHOP — Make, Repair, Buy, Sell and Exchange Violins, Bows, Cases and Strings" (St. Mary's University Rattler archive, https://commons.stmarytx.edu/cgi/viewcontent.cgi?article=1066&context=rattler) corroborates the sole-proprietorship at filing.

Unusual patterns check:

• No co-inventors, therefore no "all inventors departed within 12 months" signal — that pattern requires a team and a corporate assignee, neither of which exists.
• Consecutive-serial sibling filing (mild notable pattern, benign). Callier filed two applications on the same day: Serial No. 277,218 (this patent) and Serial No. 277,219, which issued as US 1,760,343, "Tailpiece for stringed musical instruments," granted May 27, 1930 (https://patents.google.com/patent/US1760343). Consecutive serial numbers indicate both were filed together on May 12, 1928, from the same shop and almost certainly through the same prosecuting attorney. This is a single-inventor filing-pair, not a portfolio built for liquidation — there is no third-party interest, no continuation chain, and no later family member filing.
• No fire-sale precursor. The inventor continued practicing until his death in 1971; the business passed within the family (son Paul Callier) and then to an employee (see below). Nothing suggests the assets were ever packaged for sale.

Original assignee

There is no original assignee. US 1,764,548 issued to Frank J. Callier as an individual, with no assignment to any company. Google Patents records Original Assignee and Current Assignee as "Individual" (https://patents.google.com/patent/[US1764548A](/patent/US1764548A)/en) — that is Google's placeholder meaning no assignee of record, and it should not be read as the name of an entity.

The patent's own bibliographic line — "FRANK J. CALLIER, OF SAN ANTONIO, TEXAS" with no "assignor to" clause — is the authoritative confirmation.

Data-quality flag (do not misread): FreePatentsOnline renders the sibling patent US 1,760,343 with "Assignee: Callier, Frank J." (https://www.freepatentsonline.com/[1760343](/patent/1760343).html). That is that database's convention of listing the inventor when no corporate assignee exists. It is not evidence of an assignment, and it does not contradict the finding above.

Did the "assignee" ship a product embodying the claims?

• Primary line of business: retail/repair violin shop and self-employed luthier and bow maker — instruments, bows, cases, strings; repairs, restoration and bow rehairing.
• Product practice: the shop's trade was making, repairing, buying and selling violins, bows and fittings, so the subject matter (a violin tail-piece string fastener) sits squarely in its practice area, and a fastener of this type is plausibly the kind of fitting a 1928 shop would make or install in-house. I found no evidence of mass manufacture or catalog distribution of the claimed device as a discrete product. Treat "practiced in-house" as plausible, not established.
• Current status of the business: still operating, under successor ownership. It is a continuous family/employee lineage: founded by Frank J. Callier (St. Louis 1900 → San Antonio 1916 → Hollywood 1928); taken over by his son Paul Callier; sold to Craig Scollard in 1984; now trading as Callier-Scollard Violins in the Green Hotel, Pasadena, CA (https://www.cs-violin-shop.com/about-us.html; https://www.violinorum.com/us/violin-makers/violin-makers-pasadena-ca/). It is a continuing going concern, not a dissolved entity.
• No bankruptcy, no acquisition by a third party, no IP-holding spinoff. Contrary to the "fire-sale" pattern, the patent-owning enterprise survived intact — it just never held a corporate form.

Assignment timeline

The USPTO Assignment Center has no records for US 1,764,548. I searched by patent number (1764548), by application/serial number (277218), and by assignor name ("Callier, Frank"), and matched against the Google Patents legal-events feed for the same document. Results:

Consequently there is no reel/frame, no conveyance type, no assignee LLC, and no correspondent of record to report for this patent — the correspondent-of-record tell you asked me to capture does not exist here because no assignment was ever recorded. There is also no correspondent to flag as a repeat player.

Escaping caveat on the negative (please carry into any opinion): per the USPTO's stated coverage, the online database runs from August 1980 forward. A hypothetical assignment executed in 1931, 1940 or 1946 would not appear unless re-recorded post-1980. Google Patents would likewise not surface it. My "no records" finding is a finding about the online record, not a certified pre-1980 title chain. A conclusive statement requires a manual Patent Assignment Abstract of Title / paper-record search. I am not able to assert the pre-1980 negative with high confidence.

Why the absence is the substantive answer: US 1,764,548 was owned by its sole inventor from filing until the term ran out on June 17, 1947, and the inventor died in 1971. There is no post-expiry residual asset (an expired patent is unenforceable and cannot be asserted), and no reissue or continuation was recorded. The ownership chain is a single node.

Timeline diagram

timeline
    title Ownership of US 1764548
    1928 : Filed by Frank J Callier as individual
    1930 : Patent issued to Callier
    1947 : US patent term expired
    1971 : Inventor Frank Callier died
    1984 : Callier shop sold to Craig Scollard

Note: only the 1928 and 1930 entries are patent-ownership events. 1947 is the term lapse, 1971 the inventor's death, and 1984 the transfer of the violin-shop business (which by then held no enforceable patent rights). No assignment of the patent by any party appears anywhere in the chain.

NPE / troll-pattern signals

Verdict

Insufficient data — no recorded assignments exist for this patent (0 results on patent-number, application-number and assignor-name searches; Google Patents shows no assignment legal event between the 1928 filing and the 1947 expiration).

Justification: the Assignment Center returns no reel/frame entries, so there is no transfer, no correspondent, and no assignee sequence to score against the eight NPE patterns — and for a patent that expired June 17, 1947, roughly 79 years before today, the absence of NPE activity is expected rather than anomalous. The affirmative finding, stated as strongly as the evidence allows, is that US 1,764,548 was inventor-owned (Frank J. Callier, individually) from filing to term lapse, with all eight NPE signals not present; the single material qualification is that the USPTO's online assignment coverage begins August 1980, so a definitive pre-1980 title chain would require a paper-record search rather than a web lookup.

Verification links:

• USPTO Assignment Center: https://assignmentcenter.uspto.gov/ — search Patent Number 1764548 (legacy interface: https://assignment.uspto.gov/patent/index.html)
• Patent document: https://patents.google.com/patent/US1764548A/en
• Sibling patent, same-day filing (Serial 277,219): https://patents.google.com/patent/US1760343

I'll research the prior-art citations for US 1,764,548, checking both backward citations (prior art cited during prosecution) and the forward citation records.

Let me examine the original patent PDF front page for the examiner-cited references, and check the prosecution-related records.

I found a key lead — US 10,199,015 cites a Callier reference plus US 1,337,793. Let me dig into the specific citations and the "similar documents" prior art.

Prior-Art Analysis — US 1,764,548 (Callier)

Method and a necessary correction of framing

You asked me to "look at each patent citation for 1764548." Before mapping anything to § 102, I have to be precise about what citations actually exist for this number, because there is a real risk of over-reporting here.

I searched USPTO-facing sources (Google Patents US1764548A record, patentimages full text of the original 1930 grant) and litigation/docket sources. The result:

US 1,764,548 has no examiner-cited "References Cited" list. The fetched full text of the grant (the authoritative source in the task prompt) contains no "References Cited" section, and the Google Patents US1764548A record shows zero backward patent citations. This is consistent with 1920s–30s USPTO printing practice, in which the references relied on by the examiner were not reproduced on the printed patent front page. Consequently:

• There is no official IDS / "cited-by-examiner" prior-art list for this patent that I can enumerate or certify.
• Everything I can map below comes from two non-authoritative buckets on the Google Patents record: the "Cited By (2)" forward-citation table, and the "Similar Documents" list (25 items). Those are algorithmic/annotation artifacts, not legally cognizable citations and not necessarily the art the examiner considered.

I flag this explicitly rather than silently presenting the "Similar Documents" list as the prosecution prior art — that would be an overstatement.

Cross-reference to earlier sections (no contradiction): the prior "Patent summary" section already listed the two forward citations (USD624113S1, US11501743B1) and noted the OCR artifact "1$764,543" — that artifact is 1,764,548 and I do not treat it as a second document. One new finding below (Callier's second patent, US 1,760,343) is flagged as a potential same-inventor relationship; it does not contradict the earlier sections.

Legal framework caveat (important)

US 1,764,548 was filed May 12, 1928 and granted June 17, 1930 — i.e., well before the 1952 Patent Act took effect (Jan. 1, 1953). Its validity was governed by the pre-1952 statutes (R.S. §§ 4886, 4892, 4920), not by the statute you asked me to apply. Accordingly:

• The critical reference date for § 102(a)/(b)-type analysis is the date of invention, which absent evidence is presumed to be the filing date, May 12, 1928. Only references publicly available before that date are true prior art.
• Modern § 102(a)(1)/(a)(2)/(e) categories (and AIA "effective filing date" rules) did not exist then. I apply the modern labels below only as an analytical convenience, with the pre-1952 caveat attached.
• The patent expired June 17, 1947. It cannot be invalidated today, so any § 102 mapping here is retrospective/illustrative only.

Bucket 1 — Forward citations ("Cited By") — not prior art

These post-date the patent and therefore cannot anticipate anything in US 1,764,548. Listed for completeness because they are the only citations the record actually shows.

Bucket 2 — "Similar Documents" list, split by date relevance

The 25 documents split cleanly on the May 12, 1928 critical date. Only the six items dated before 1928-05-12 can be § 102(a)/(b)-type prior art; the rest are either same-era-but-later publications or far-modern art.

2A. Pre-filing references — the only potential § 102 art (highest priority to investigate)

2B. Post-filing, same-era references — not § 102(a)/(b) art (filed/published after 1928-05-12)

2C. Modern references — not prior art to a 1928 filing

US 3,596,552 A (1971, "Devices for securing strings in musical instruments"); US 3,933,077 A (1976); US 4,040,830 A (1977); US 4,320,685 A (1982); US 6,982,372 B2 (2006); JP 2007-537471 A5 (2008); US 7,692,080 B1 (2010); US 7,893,329 B2 (2011); US 9,355,622 B2 (2016, "Anchoring system for a string in a musical instrument"); US 10,262,635 B2 (2019). Also US 2,469,582 A (1949), US 2,486,549 A (1949), US 2,824,478 A (1958). All post-date the patent by decades; none can anticipate.

Special note — US 1,760,343 ("Tailpiece for stringed musical instruments")

This is the one genuinely new finding worth surfacing. In the reference list of US 10,199,015 B2, adjacent entries appear as:

• 1,337,793 A * 4/1920 Poehland ...... G10D 3/12 84/302
• 1,760,343 A * 5/1930 Callier ......

Two things follow:

1. US 1,337,793 (Poehland) is being used by later examiners as the closest G10D 3/12 art — reinforcing it as the top § 102 candidate against US 1,764,548.
2. US 1,760,343 is attributed to Callier — the same surname as this patent's inventor, Frank J. Callier. If it is the same inventor, then US 1,764,548 and US 1,760,343 are co-pending same-inventor cases in the same art, raising (a) a possible double-patenting / same-family relationship and (b) a possible earlier-Callier-application reference. I could not confirm the inventor identity, common ownership, or US 1,760,343's filing date within this session, so I state this as a lead, not a conclusion. Note the prior "Patent summary" section listed US 1,760,343 only as a neutral "Similar Document," so this attribution is an addition, not a contradiction.

Bottom line on § 102 anticipation

No reference on the record is a confirmed § 102 anticipation of claims 1–5. The strongest candidate, US 1,337,793 (Poehland), is a fastener for tailpieces in the same classification (G10D 3/12) and would be the first document to pull and read against claim 1/claim 4.

Honest limits

• As fetched, US 1,764,548 carries no examiner citation list; I could not retrieve an IDS or examiner's "references cited" from the 1930 file. The mapping above rests on Google Patents' "Similar Documents"/"Cited By" annotations, which are not legal citations.
• I did not retrieve or read the full text of the six pre-1928 references in this session. Their descriptions come from title/date/classification, so the § 102 claim mappings are provisional and must be confirmed against each reference's actual disclosure.
• The OCR artifact "1$764,543" is the same document as 1,764,548; I have not treated it as a separate reference.
• For a definitive prior-art set, the authoritative next steps are: (1) pull the original USPTO PatentCenter PDF of 1,764,548 and any available 1928–30 file-wrapper contents; (2) retrieve full texts of US 1,337,793, US 1,416,568, US 336,428, US 516,125; and (3) verify the inventor/filing date of US 1,760,343.

I'll ground this analysis in the prior-art references listed on the patent's own page. Let me pull what I can on the key candidates.

Good — I now have solid content on four of the listed references. Let me firm up two more that bear directly on the "bent lug clamping opposite faces" concept.

Obviousness Analysis — U.S. Patent No. 1,764,548 (Callier)

0. Threshold caveat on the governing statute

US 1,764,548 was filed May 12, 1928 and granted June 17, 1930. 35 U.S.C. § 103, by its terms, applies only to applications filed on or after January 1, 1953. Strictly speaking, this patent was examined under the pre-1952 "invention" standard (R.S. § 4886 / § 4920, as construed in Hotchkiss v. Greenwood and later Cuno Engineering v. Automatic Devices). I flag this because it is the single largest methodological issue: an "obviousness" rejection in the modern sense was not available against this application.

That said, the requested analysis is coherent and useful, because the Graham v. John Deere framework is the codified descendant of the pre-1952 inquiry. I therefore run the analysis under § 103 as a lens, and note where the pre-1952 standard would have reached the same or an easier result (the "invention" standard was, if anything, more demanding on the applicant than § 103 — a mere "new and useful" mechanical combination would have failed Hotchkiss).

Applicable prior-art window. Under R.S. § 4886 as amended in 1897, the statutory bar runs from May 12, 1926 (two years pre-filing), and the "before the invention thereof by the applicant" limb runs from the (unstated) date of Callier's invention, presumed on or before May 12, 1928.

1. No contradiction with the earlier sections

The bibliographic, claim-construction, and litigation sections stand. Two cross-references I rely on and do not repeat:

• The claim-reconstruction caveat (two-column OCR jumbling of claims 1 and 5) applies to this analysis; I treat the five-claim structure as reconstructed there.
• The note that US 1,760,343 (Callier, "Tailpiece for stringed musical instruments," published 1930‑05‑27) shares the same inventor and the same May 12, 1928 priority date as the patent at issue. It therefore cannot be § 103 prior art against US 1,764,548 (same inventive entity, no earlier date). Similarly, the 1931 documents in the "Similar Documents" list — US 1,791,977, US 1,803,661, US 1,884,434, US 1,750,019, US 1,755,170 — post-date the May 12, 1928 filing and are categorically unavailable as prior art (Seckendorf's US 1,791,977 was filed Nov. 20, 1928, after Callier's filing). Any obviousness analysis built on those would be defective.

(Housekeeping: the task header gives April 26, 2026, while the retrieval environment reports September 28, 2026. No effect on this analysis, which is date-independent.)

2. Person having ordinary skill in the art (PHOSITA)

A mechanical designer or instrument-hardware maker with a few years' experience in (a) violin‑family tail pieces and string‑anchoring hardware and (b) sheet-metal stamping and bending for musical-instrument fittings. No engineering degree required. This is a mature, crowded, small-goods art with well-known forming techniques (striking up tabs, slitting, bending, notching) — the art of Son (1894) and Grover (1926) below.

3. The prior art of record

4. Claim-by-claim analysis

Claim 1 (violin; through-body + angular abutment + slit-defined anchor and bendable lug)

No single reference anticipates. The differences over the art are: (i) a body that passes through the keyhole slot; (ii) an angular abutment bearing the underside; (iii) a longitudinal incision opening through the free end splitting that end into an anchor tab and a bendable lug; (iv) the lug bent onto the upper side to clamp.

Each element is separately old, and the combination is a predictable mechanical assembly:

• Perry (336,428) supplies the substrate: a one-piece, bent, longitudinally slotted metal plate for a violin tail piece. Perry already teaches that a single metal blank can be bent at an angle and slit lengthwise.
• Grover (1,589,755) supplies the operative principle that is the heart of claim 1: a struck-out, bendable lug bearing on an adjacent surface to prevent the part from being raised by the pull of the strings. Substitute Grover's banjo rim for the violin tail piece's upper face and the claimed "lug in pressure engagement with the upper side… cooperating with said abutment" follows directly. Grover also teaches the L-cross-section ("plates… at right angles to each other") and right-angled string-holding projections.
• The admitted keyhole-slot tail piece supplies the environment and the datum surface; the specification's own advantage — attaching "without modification of the tail piece" — is a constraint the art had already met (Poehland's hooks engage the existing holes; Grover states its piece attaches "without modifying the structure of the device").
• Mazzocco (1,416,568) supplies the notion of a separable metal element passed through a slot in the tail piece and separately retained per string, in a metal-string context.

Motivation. All references are in the same field and address the identical problem: retaining a string against tail-piece tension without gut tying and without altering the tail piece. Poehland (1920) and Grover (1926) document an express, market-driven demand for add-on metal string fixtures for exactly the wire strings the patent's own specification says musicians prefer for the A and E positions. A PHOSITA seeking to seat a metal E or A string in an existing keyhole slot, aware of Grover's lug-and-opposite-face hold-down, would have been led directly to a slit-and-bend tab that clamps the tail piece from above and below.

Result is predictable, not unexpected. Under KSR, "the combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results." Nothing in the claim produces a new function; it produces clamping.

Claim 2 (adds one rear-edge string notch)

Son's cross bar notches (a³) "receive and guide the strings." Notching a string-retaining tab is the routine expedient of the art; substituting a notch for Mazzocco's eyelet is a predictable substitution of one known string-retainer for another. Obvious over the claim 1 combination + Son.

Claim 3 (a plurality of selectively engaged notches)

Two notches on one tab is the duplication of a known part to accommodate two known use positions. The specification supplies the entire rationale and it is a fact about the prior-art instrument, not an inventive insight: "The tail piece is thicker at the A string position and the lower notch 18 would be below the surface of the tail piece." Any violin maker knew the A and E positions differ in tail-piece thickness. Duplication of parts to fit two standard stations has no patentable weight, and there is no asserted unexpected result. Obvious over claim 1 combination + Son.

Claim 4 (generic stringed instrument; "formed from flat metal"; lug and abutment engaging opposite sides)

Formally the broadest claim, but functionally the thinnest: the only material addition over claim 1 is the express "formed from flat metal" limitation and the removal of the violin-specific sides. Flat, single-piece stamped metal is squarely disclosed by Son ("made preferably of metal and stamped out of a single piece") and Perry ("a bent metallic plate"). The "opposite sides" engagement is Grover's lug-against-rim principle generalized. Obvious over Son (or Perry) + Grover + the admitted keyhole-slot tail piece.

Claim 5 (anchor extends above the lug + string-receiving notch)

"Extended above the lug" is the inherent geometry of any slit-and-bend tab where one slit portion is left standing and the other is folded down — precisely the arrangement of Son's struck-up, bent-back string fingers (a⁴) and Perry's single-piece slotted plate. The notch is Son's a³. Obvious over the claim 4 combination in view of Son.

5. Graham secondary considerations

• No objective evidence of record. The earlier sections found no litigation, no assignment, no licensing activity, and no commercial-success record. The only forward citations are 2010 and 2022 design/utility documents — citation relationships, not evidence of deference by the art.
• No long-felt-need evidence. The "need" recited in the specification (metal A/E strings, no tail-piece modification) had already been identified and addressed by the art years earlier — Poehland 1920, Mazzocco 1922, Grover 1922/1926. A need that others met before the applicant is not a long-felt need.
• Stated advantages carry no weight. "Highly simplified construction, neat in appearance and cheap to manufacture" are the routine design objectives of the art, and pre-1952 precedent gave them essentially no weight.
• No unexpected results asserted anywhere in the specification for the two-notch arrangement.

6. Bottom line

Conclusion: Every claim of US 1,764,548 would have been obvious under § 103 over the enumerated combinations, and — on the pre-1952 standard actually applicable — would more likely than not have failed Hotchkiss/Cuno as a mere new arrangement of old mechanical elements in a crowded art.

7. Confidence and limits — read before relying on this

1. Statutory mismatch. § 103 is not the correct governing statute for a 1928 filing (see § 0). Presenting a § 103 analysis is analytically useful but legally anachronistic.
2. No drawings inspected. I worked from retrieved text and abstracts. Perry's single-piece slotted plate (Fig. 1) and Son's struck-up finger structure (Fig. 3–4) are the two most load-bearing disclosures, and I have their descriptions but not their figures. A claim chart against the actual drawing sheets is required before treating any rejection as final.
3. Weymann US 1,615,152 is the softest reference — its content comes from a 1927 trade-press abstract, and I have not verified the patent text. It is not essential to any combination above.
4. Grover date nuance. US 1,589,755 granted June 22, 1926 — five weeks after the May 12, 1926 two-year bar date — so its statutory-bar qualification rests on the documented 1922 public use/on-sale of the Grover extension tailpiece, not on the grant. If a challenger relies solely on the patent date, it must also establish Callier's invention date is on or after June 22, 1926.
5. The two genuinely unavailable "similar documents" (US 1,760,343 and the 1931 references) must not be used; using them would have produced an invalid rejection.
6. I did not locate any reference expressly disclosing the precise claimed combination; this is a combination/obviousness conclusion, not an anticipation conclusion.