A sweet vintage ring. It's sterling silver, with spinel and aquamarine stones. This may have been a customizable piece, as the stones are in separate settings that are screwed onto the ring (and look removable still).
Marked "Sterling". One of the stone settings is loose, I have not attempted to tighten the screw holding it on, you'd need a very small screwdriver. About a US size 8.
I am always happy to answer any questions or send more photos when needed.