Silver banded Agate pair of cufflinks

I show you this pair of silver banded Agate cufflink. The agates have quite a large size ( 2 x 1.5 cm) and a nice banded pattern in golden brown, black and white. The have, as you can see on the photo's four marks. Two of them are the French lobster/crab. This hallmark used from 10 Mai 1838 on for small objects and fineness 800/1000. The other mark is 835 for silver and there is a hallmark for the maker which I think to be an S t than a little four pointed figure and SB. Perhaps maybe someone of you can tell me who this craftsman could be ??