2-headed cameo

Hi.Can you tell me anything about this cameo? There are two heads, a man (a Roman, I believe )in front of a woman. I had it taken to an antique jeweler and she could not date it. I believe it came from the old country (England) a few generations back, and from a family of 'old money,' and I believe it to be of great value.....hmmmm. thank you for any info you can give. Kjc