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.