Does anyone know when (or approximately when) the word "patent" began being stamped on British-made metal objects? I am trying to establish whether the age a brass artifact found in a gatepost hole is consistent with a 1770's-1780's time period suggested by other diagnostics found in the same hole. The artifact, which may be part of a hasp, has stamped into it a crown, the initials "G B" and the word "PATENT". The "G B" indicates that it was patented, if not manufactured, during the time of the Four Georges, which could take it up into the early 19th Century. 

Dave Shonyo
Gunston Hall Plantation