The hallmark is a London mark from 1764. Unfortunately the maker, BB, is unknown. The mark does not appear in any of the existing London registers of makers' marks, but there are 2 registers missing, one for largeworkers covering 1758 - 1773 and one for smallworkers covering 1738 - 1758. We presume that BB was originally listed in the first of these registers. I have previously seen examples of this mark dated 1762-1765.