Cameos can be made from many kinds of layered stone and have been for a couple thousand years. they are also made from shells including some mother of pearl shells.
The above cameo and many others with the same look are made from shell, but not MOP.
The traditional cameo shell of Italy is the flame or bullmouth helmet cassis rufa found on the African coast and commonly called the "carnelian shell" after one of the original cameo stones, the carnelian. Many other shells with 2 layers are also used.