Silver Finish Locket Watch Fob

This "book style" locket fob features black glass (or onyx) on one side and on the other what once might have been a silver horse head in a matrix of mother of pearl. The locket spins within the frame to open or change sides. The side with the pearl is well worn and in addition to the wear on the horse head is worn through to the brass in a couple of spots on the frame. It measures 1 1/2" long and 3/4" wide. This lovely early fob probably dates from the 1850's.