What period or age is this cameo I found at an estate, and where can I sell it at a fair price.

by Steve
(Fl)

I purchased this cameo from an estate. From what I know it is sardonynx. The carving depicts Mars riding a chariot on some clouds. When held up to the light it appears reddish brown. There are no cracks or hairlines. I had it tested by a reputable jeweler and it tests 14k and is surrounded by approx. .80ctw diamonds. The pin back appears old C-type hook. The pin looks almost as if it were forged not soldered. The only marking I could find looks to be a capital AP at the base of the pin back. So what do you think? I'll try and send a few photos. Thanks.