Between 1896 and 1934, patent offices in at least nine jurisdictions received specifications for bent-wire devices intended to hold sheets of paper together. The Brennholt Institute of Applied Taxonomy has read 214 of them. Its conclusion is narrower than the popular one, and more useful: the early patents describe machines, variants and methods far more often than they describe a fastener, and the form now in general use is not the subject of any claim in the Institute's sample.
The Institute names no patentee on this page, as it names no inventor anywhere. A patent records what an applicant asked to have protected. It does not record who first made the object, and it is frequently silent on whether the object was ever made at all.
The 214 specifications were assembled between October 2024 and June 2026 from published patent gazettes, abridgement volumes and the indexes of three trade directories. The Institute admitted a specification to the sample if its claims concerned a device formed from a single length of wire, intended to hold two or more sheets, and not piercing the paper. Specifications for pins, staples and spring-steel clamps were excluded. Brindlecott estimates the sample at between 60 and 75 per cent of all qualifying filings in the period; the Institute's review panel considers the upper figure unsupported.
Each specification was classified by the subject of its principal claim, in one of five categories:
| Code | Subject of the principal claim | Specifications | Share |
|---|---|---|---|
| PC-A | A fastener of a defined geometry | 71 | 33% |
| PC-B | A machine for forming fasteners from wire | 58 | 27% |
| PC-C | An improvement to an existing fastener (a tongue, a rib, a bent tip) | 49 | 23% |
| PC-D | A method of use, packaging or dispensing | 24 | 11% |
| PC-E | A combination with another article (a tag, a label, a file) | 12 | 6% |
Only the first category claims a fastener as such, and only 71 specifications fall within it. Of those 71, the Institute could match 19 to a form documented in its own register of wire-formed fasteners. The remaining 52 describe geometries that appear in no trade catalogue the Institute has examined, and Brindlecott treats them as proposals rather than products.
The symmetrical double loop, coded WF-2 in the register and documented in catalogues from 1901, appears in the sample only as prior art. It is drawn, in eleven specifications, as the thing the applicant intends to improve. It is claimed in none. The offset double loop, WF-3, is in the same position.
Brindlecott reads this absence as evidence that the dominant form was already in the public domain when the patent record begins to describe it: an applicant cannot claim what the examiner already regards as known. The review panel accepts the observation and rejects the inference. Its note of 14 January 2026 argues that a sample of 214 cannot establish the absence of a claim, and that a single unexamined specification would overturn the conclusion. Brindlecott agrees that it would, and has asked that the conclusion be read with that condition attached.
The 58 machine specifications are, in the Institute's view, the most informative part of the record. They describe feed rates, bending sequences and cutting methods, and several state an output per hour. The figures claimed rise from roughly 3,000 fasteners per hour in the earliest machine specification in the sample, filed in 1899, to more than 40,000 per hour in a specification of 1928. Brindlecott's position is that the paperclip became an office object through this increase in output, not through any single geometry, and that the patent record supports a history of manufacturing capability rather than of invention.
The taxonomist of Kettering disputes the use of claimed output as evidence, on the ground that applicants had every reason to overstate it. The Institute records the objection and has not revised the figures, which are reported as claimed and not as achieved.
None of the 214 specifications claims a dimension. Several give an example length or wire thickness in the description; none makes a size part of the protected invention. No national standards body has ever ratified a diameter class for the office paperclip, and the patent record offers no substitute: the early applicants protected shapes and machines, and left the question of size entirely open. Brindlecott's seven-class system remains the only published attempt to close it.