Vintage Sterling Silver Reversible Black Onyx & Mother of Pearl Marcasite Pendant. The oval section swivels around putting the Onyx or MOP to the front. 

It's in excellent condition with surface wear. 

It weighs 5.8 grams. It measures 1 1/16 inches top to bottom and 5/8 inches wide. The bail will fit up to 3mm. 

Pv2154.