This is a beautiful, large shell cameo from the Edwardian era of a Bacchante maiden set in a lovely 10K gold chased setting. She is very nicely carved with grapes in her hair to indicate that she is a follower of Bacchus the god of wine. The pin catch is marked 10K and also has a maker's mark that I haven't been able to identify. It can be worn as either a pin or a pendant as it also has a fold down bail at the top.
The cameo measures 2 inches by 1 3/4 inches and it is in excellent condition with no cracks or other damage.