you have 
This is beautiful . This is a shell Cameo in a Sterling setting that can be worn as a pin or it has a loop for a chain so it can be worn as a pendant . You need a chain. The pin is about 1 1/8 x 7/8 " in size . This is signed to the bottom back ,but we cannot make it out . It does test Sterling . The metal is dirty . This does need a cleaning. It is beautiful . Excellent Condition.