any chance of seeing a photo of this ring? the mark you have described, sounds like one of marks used by the company Goldsmith Stern & Co of 33 Gold St. New York City. I believe they stopped trading in the 1930s. They were famous for their thimbles.
Compare the mark on the ring with the jewelry marks of Goldsmith Stern & Co in the link - "US Jewelry Marks 1922" in the Antique Jewelry Investor Jewelry Resources. They are listed alphabetically.
