This is a very nice vintage Art Deco lavalier pendant. It has a geometric form typical of the Art Deco era with and etched design and it is set with an oval faceted clear yellow glass stone. It is marked 1/20 12K on the back of the pendant and it looks as if it could be silver underneath the gold fill, but I didn't want to risk damage by testing it. The chain is unmarked, but appears to be original.
The pendant is 1 1/2 inches long and 7/8 inch wide at its widest point. The stone is about 1/2 inch long. It is suspended from a chain that is 18 inches long. It is in very good condition. I don't see any flaws in the stone. The metal has some areas of tarnish and there is some wear to the finish on the chain.