A hallmark is a set of marks made on a piece of precious metal to indicate it's quality, as verified by a particular assay office.
The hallmark normally contains - an indication of the controlling assay office (a national body, or a local one for a city or region) - the type and quality of the metal - the manufacturer - and frequently an indication of the date of manufacture. Naturally this information is of great interest to the dealer in antiques and jewellery. Naturally therefore they are also prone to being forged. For a long time then, the stamps used to make these marks were very fine pieces of the metalworker's art, to discourage copying by unauthorised people. Again, this makes them a target for forgery.
I have been examining a ring which I brought from a jewllers as Oksana's engagement ring. I got the size drastically wrong - it was the first ring I ever brought - and it has long needed to be rebuilt to fit her much smaller fingers. And in the process, I've been examining the hallmarks.
- the 4th character is a 5-petaled Yorkshire rose - which is the symbol for the Sheffield assay office.
- the boxed "375" is the gold count in parts per thousand. 375/1000 is 3 parts in 8, or 9-carat.
The rest of the symbols - I need to take a closer photo (and the ring is currently at the jewellers), or get the sketchbook and loupe out.