This is a stainless steel ring.
Signed/marked but I don't know the maker. Looks like SD (connected with a v).
Ring size looks to be a 7
The ring top is about 3/4 inch in size.
 

Good used vintage condition; might need some light cleaning/polishing and have some normal age ware.

Because my items are vintage/used they may have some signs of use/wear and/or be in need of some cleaning or polishing. I have not tried to clean or do anything to the piece.