Found another ring with a mark of a ( u over a arrow ) looked it up it says.
uncas mfg.co Rhode Island 1911 - present.Large manufacturers of sterling and costume jewelry this mark was introduce in the mid 20s. It does say sterling on it .
The question is would it be sterling.
STERLING = 92.5% SILVER
Prior to the 1880's, jewelry was sometimes made from what was considered Coin Silver.
COIN SILVER = 90% SILVER
Congrats on a nice find.