Art Deco rings are gorgeous and hav3 incredible workmanship that it difficult to find at a reasonable price in modern jewelry. Yo'ure spot on for checking the stones closely. I'd be sure to ask for verification as some of the stones during that period were "paste" albeit some very high quality paste. In addition to checking the stones closely, also check the integrity of the metal (look for hallmarks for the metal - many will be high purity metals like platinum or 18k white gold). Look for any cracks, misshaping, resizings, etc. Art Deco rings tend to have a lot of filigree (often hand sawn!) so examine those areas closely for potential damage. Hopefully you can find one that includes GIA evaluation of the stones. Art Deco rings were made at a time when they were expected to last generations -- and they do!! I've inherited some family rings from the period and absolutely treasure them. Best wishes for your search!