Adorable little 15 carat gold locket, decorated with an applied red enamel six pointed star, the centre set with an old cut diamond (approx .15 carats)
 
The locket opens to reveal a vacant compartment for you to add your own memento.
I'm guessing it would have had a glazed panel, but that is not present.
 
Looks great hanging from a fine chain, or hung with a cluster of charms
 
weighs - 4.9g
diameter - 16.1mm 
no hallmarks, tests as 15 carat
good antique condition