After a chat with Lindsay about how to verify that an ancient cameo is, in fact, thousands and not hundreds (or dozens) of years old, I can say this: our mentor, the dealer who taught us everything during the early years of our pivot into antiques, offered to buy it from us. "Name your price," they said, "it's just so right." When an English dealers says something is "just right" it means there are no suspect details that indicate it's reproduction. We didn't sell it, and Lindsay wore it for years. We're all dog lovers here; so were the ancient Romans. I wonder what this guy's name was. The 18k gold mounting is more contemporary.
MATERIALS: 18k gold (tests), agate
AGE: c. 2-3rd c. AD cameo, more contemporary mounting
CONDITION: Very good - minor surface wear commensurate with age and use
SIZE: 7.75, can be resized; 3/4" x 5/8" head, just shy 1/8" shank