Details of availability are given on our science publications page . Allowing for these problems it would appear that some patent references cannot be identified anyway. It is possible that these represent fraudulent patent numbers, used to discourage imitations. Before 1916 filing numbers and published patent numbers were the same, and the year is needed as well to identify the patent. From 1916 onwards the year is not needed for the patent, but they are necessary if the only information available is the filing number.
Artefacts can indicate their patent numbers in a variety of ways.
The surname of the inventor, or the company name, is often on the older artefacts which assists identification. Sometimes the number is only on the packaging. Some artefacts bear application numbers although the patent was never granted. Some artefacts will not bear any information concerning relevant patents. There has never been a prescribed way of citing a patent on an artefact.