Can you help me identiy the design style and history of my 1920s white gold ring, single center diamond, that's stamped with a crown marking?

by AF
(Boston, MA, USA)

Hello,

I recently purchased in NYC a 1920 vintage 14K White Gold Oval Ring with a .30 diamond in the middle. The band has a crown stamped into it that looks like a funny W. I was told by the seller that the ring came from a duchess' estate, but the seller could not tell me which duchess. I'm trying to figure out the exact design style to call this ring (i.e Edwardian, Art Deco, ect...) and how I maybe able to identify the duchess or whom the ring belonged to. Just trying to understand a bit more about the history of the ring, any help would be appreciated!

Regards,
AF