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I need your help frens, looked everywhere to identify those hallmarks on a set of silverware i recently purchased, but i couldn't find anything.
It's seems to depict
>crowned eagle on left side and a key on right side
>the letters "FB" with a crown on top and a star/inverted pentagram below

My guess is it could maybe be 18 or 19th c. german silverware with the eagle being a city mark, but i couldn't match any city i could find. On one of the fork there is what i believe to be the zigzag typical of old german silver testing essays. But it's almost completely gone and don't even show up on pics.
The tableware in question is heavy uniplat style, typical of mid-18th c. silverware.