A Correction on Canadian Patents (Dating Guide Addendum)

The Dating Guide Addendum is a correction note added after the fact to the established guides used for dating Dunhill pipes. Its subject is narrow but its consequence is directly practical: the number and validity range of two patents registered in Canada turn out to differ from what the guides had said. The correction rests not on interpretation but on documents; the summary records in the online patent database of the Canadian Intellectual Property Office redraw the range a stamp can point to. For the general role of patent stamps in dating, see the entry on pipe patents.

The Vernon Joint and Registration No. 325.090

The Vernon joint is a threaded tenon mechanism used where the mouthpiece meets the shank; records say it was introduced in 1931 and is seen up to the Second World War. Its Canadian registration has at times been given in guides as 356.090, but the number in the official record is 325.090; the discrepancy is explained as a typographical error arising from transposed digits. The record defines the patent under the heading "mouthpiece for tobacco pipes and the like."

The real correction is in the date. While the guides had assumed the registration dated to the mid-1930s, the CIPO record gives the grant date as 16 August 1932, and the end of the protection period as 16 August 1949. Under Canadian practice of the period, protection ran seventeen years from grant, so the two dates confirm each other. For a collector, the result is concrete: a pipe carrying this stamp can be dated a few years earlier than the guides had indicated. The upper bound, on the other hand, is not equally reliable; there is no evidence that production continued through to the end of the protection period, so 1949 is not a closing year but, at best, an upper frame.

The Flanged Inner Tube and Registration No. 197.365

The second correction concerns the flanged inner tube fitted inside the shank. The guides place this stamp in the range 1927–1941. The CIPO record, however, points to a different table: registration no. 197.365 was granted on 17 February 1920 and lapsed with the end of its seventeen years on 17 February 1937. The record's title is a general phrase, "tobacco pipe and cigar holder," so the information tying the number directly to the flanged inner tube comes from guide tradition. Set side by side, the two ranges produce a considerable shift in the earliest and latest years the stamp could be expected to appear.

The reason for the shift is not clear. The common explanation is that the older Canadian registration no. 158.709, for the unflanged inner tube, remained in force for a time and delayed use of the new stamp; but the year that registration expired is not consistent across sources, and the explanation isn't strong enough to carry the weight on its own. Nor is it seen as unusual for more than one registration to be used side by side in the same years: on the British side, registrations 5861/12 and 116989/17 are reported to have been used together for a period. In this case, the most measured conclusion is that the stamp may be seen within the protection period, that is between 1920 and 1937, on pipes headed for the Canadian market.

The Correction's Value for Dating

These two notes do not replace a guide on their own; they are footnotes added to the margins of the existing guides. The lesson they carry, though, is general: a patent stamp shows not the year of manufacture but the range during which the registration was valid, and that range can only be tested against the official record. For a comprehensive reading of Dunhill stamps, the Dunhill patent stamps and Dunhill dating entries should be read together. As new examples surface, these ranges can be expected to narrow further still.