I was looking for more information on a bracelet and earring (one missing) roman soldier/gladiator jewelry that belonged to my Mom, identical to how your ring looks. The bracelet is made up of seven circular cameos linked together. My Dad was in the US Navy and on a Mediterranean cruise in the early 1950's. I remember my Mom always having these pieces of jewelry so I suspect my Dad brought them back about 1952 on his return from the Med. I know he visited Italy so strongly suspect they came from there. Not sure the material either, but they have an irredescence to them so I suspect shell. Enjoy your ring! Such a beautiful find!