Tiny Marks on a Silver Ring...help!

Hi all! I came across this little silver ring of my sister's as she was cleaning her jewelry and I'm curious about the marks on it. We're in France but she got it at a carboot sale so who knows where its from. It has what I assume is the makers mark, a purity stamp (?), and a date mark. The date mark is definitely an M in a square, the makers mark is harder to read. I believe its an S in a semi arch? All those marks are on the outside of the ring which seems odd. The inside is stamped B25 but I looked it up and there's nothing. The pictures are the best I could get with my phone as its all so tiny. I'm not expecting it to be anything special but its annoying me that I can't figure it out!

Thanks​

 

Russian and USSR marks are often on the outside of a band.

 

Interesting lead, thank you Bear!

 

Just been looking around at Russian/USSR marks but nothing looks similar to mine, unless its just been worn down that much.

 

It's hard to read the inside mark because the photo is a bit fuzzy, but are you sure it's B25, not 925 or 825?

 

I wondered about 925 as well but that does look like an 8.

 

I hadn't noticed how blurry it was until you pointed it out, sorry! I could have sworn that was a B but upon further inspection it is indeed an 8.

 

Sure looks like an 8 from here.

 

825 can be gold, you need to take it to someone for testing. Don't trust the marks, have it verified!

 

If it was indeed gold that would be a fun find! My sister got it for 50 cents, I'll tell her what you all suspect. If it were gold though wouldn't it have some weight to it? Its fairly light.

What about the other marks though? I still can't find anything...

 

It doesn't, they don't have an .825 gold fineness.

 

No worries! 825 as silver then, makes more sense to me weight wise. Still nothing turning up in regards to the other marks, very confusing.