I'm happy to answer your conservation/preservation and materials identification questions.
It's very unusual that it wouldn't be marked as "quadruple plated" or if plated on nickel silver- E.P.N.S..
All silver objects have hallmarks that identify the maker and the silver content, e.g. "Sterling", or the numbers "925" by law.
The fact that your piece isn't marked, makes sense that it is plated. You can use a small magnet to see if the base metal is ferromagnetic. If it isn't, look for areas that are darker and have a different reflectance than others. When plated pieces are overpolished over time, the plating is removed and the base metal tarnished differently.
Can you post clear, focused photos of any marks and some of the overall object in your response? That would help to confirm my answer.