Copper?, Bronze? Fork

Thought someone more knowledgeable could help with an ID/more info on this old fork. I found this last year at a colonial site (central NC) that has given up many tombac buttons and a "Fox with Tallio" cuff button someone here identified. This started out with a dark patina and also had a iron ring rusted onto the stem. When I ran it through electrolysis, it turned the copper or bronze color.

On the back I see a "BM" maker's mark, and a couple of other symbols I am unfamiliar with (British, I guess). I did some googling and the BM may stand for Benjamin Mountigue? Thanks for taking a look!