Stamped Sterling, 925,Taxco. The initials are difficult to read, perhaps R G or R C. Measures 1-1/2" x 1-5/8" and weighs 11.1 grams. Very Art Deco design to me. You'll love the glow of the Amethyst of this brooch.
Contact: Dream Jewels For You PO Box 90 Lakeside, OR 97449 541-999-9942