Large 1930's Rhinestone Pendant Brooch - Big Blue Stone

Extremely unusual construction. Chain attaches to either side of the removable pendant or pin brooch with two small flat clasps. Pendant or brooch itself is a love knot style design with a huge central stone in a stunning deep turquoise blue color. Accented by two rows of smaller clear stones, each of which is bright and clean, showing no damage or discoloration. We believe this is 1930's, but it's such a classic style that it could be a bit earlier or later. Some greenish patination is visible between the links on the chain if examined with magnification. Entire necklace is approximately 15" long. Pendant is approx. 1 1/2" in diameter. No marks as to maker, metal content, or place of origin.