Vintage Silver Tone Oval Locket With Butterfly on a Chain

1960s era locket with etched butterfly design.
Front is a satin finish with some scratches.
Double sided locket with original celluloid covers.
Nice audible snap when closed.
There is a cut out on the front center border.
This is my second locket with this cut out.
I have no idea why it is there.
Fair to good vintage condition.
Chain measures approximately 22 inches.
Locket measures approximately 1.75 inches by 1.25 inches.