Patent date

I'm sure this is a common problem, but lately I seem to be having more and more discussions/arguments with people who insist on dating their items based on a patent date. It's difficult, at times, to explain that companies, including CCM, often used the same part for many years on their products. Thus you can get a hub patented in 1937 on a 1946 bike. My latest go-round is with a gentleman who insists his CCM wagon dates from 1925 based on the patent date on the handle, when in fact that same wagon was listed in the company catalog well into the 40s with the same handle.