Silver content of 18th century Bremen groten coin (and similar vintage)

Just out of curiosity... I have this 1750 Bremen 1 groten coin (https://en.numista.com/catalogue/pieces48569.html) that only says "Silver" with no fineness specified. Does anyone know what fineness the coins of this period were generally minted from? Is it essentially billon with only a trace amount of silver?

My only coin from around that time and in the region is a 2 Schilling from Hamburg and it is on a 437/1000 billon planchet. So yours should be a bit less pure because of the smaller value in correlation to its weight. Maybe around 300/1000 if one can simply extrapolate these things .