do you think the ring might be costume jewelry? An excellent jewelry patent resource can be found at the following address: http://www.jewelrypatents.com Patenting costume jewelry was all the rage in the 1920s - 40s and declined in the 1950s. There was some high end sumtuous costume jewelry produced during this period.
I would suggest getting the stones identified - if they are cut stones, the cut can provide dating clues.
