George III silver tankard

Hi

I received for my 21st birthday from my late uncle a silver tankard (see photos). apart from it being from London and the initials B*S on the handle, I wonder if there is any history to this style / shape of tankard or if the letters might mean more than the initials of the user… could have been engraved later i suppose !

any ideas…

Thanks
tankard2.jpg
tankard1.jpg