Vintage Art Deco Style Sterling Silver Brooch with Marcasite

Vintage Art Deco style large brooch in sterling silver. It is set with marcasite and black stones that test as black onyx. It measures 2 1/2" by 1 1/16". Has a locking clasp. Pin wobbles. Weight: 18.7 grams. Missing one marcasite. No hallmarks. Acid tested. 

 See how it sparkles in the sun?