1920's Art Deco Diamond and Amethyst 14kt Brooch or Pendant

Hello,
I honestly do not remember where I bought this, but I didn't pay a lot. I just recently had it looked at, because I am thinking of listing it on eBay, but I am a little hesitant. Does anyone know of a better site to list fine jewelry?

The diamonds are 15 points each, and perhaps European. The center amethyst is real, but it is chipped. It is set in a nice filigree setting that is 14kt, signed.
Mrs. Warren