Hi I have a gold locket that I would like identified thanks

by Julie
(Hill Top Australia)

I have attached pictures, the locket has a hallmark on the back that I have provided a picture of and the marks XVIII in various places inside the locket and around the edge of the "frame" that comes out that holds the picture. I believe the stones to be rubies and diamonds and assume the 18 means 18ct gold? Any info would be helpful