Poison Ring - Fineness mark 915/815/916/816 - "Russia"

[Chronicler]

I purchased a silver Poison Ring / Box Ring titled as originated from Russia.

However, I could find only one hallmark that is clearly a finesse mark



I can't be sure but it looks like 915 or 815 or 916 or 816.

Now I was looking around the 925-1000 and found the https://www.925-1000.com/a_Standards.html

There is no 815/816 but some interesting information on 915/916.

Is it possible to find anything about the time/place of the rings making, basing simply on this one mark ?

Any help appreciated.