Your small bowl has the form of a wine taster or tastevin.
Sterling silver is an alloy of silver of a minimum fineness of 925 (92.5% by mass of silver).
Your item is 900, meaning a bit lower than sterling but still very good, having in mind the most common fineness e.g. in Austria and Germany was 13 Loth or 812/ 1000.
(You will find many items made of lower fineness 800/1000 silver).
In short, strictly speaking it`s not sterling but it makes little difference.
As for the maker and the country of origin, it`s difficult to tell based on these marks. Hopefully, members of this forum may have seen the same maker`s mark with reliable reference.
Regards