1920s - 30’s Elegant design filigree bracelet in gold with a clear, diamond-shaped center accent. Intricate openwork design offers timeless, feminine appeal. Lightweight and comfortable for everyday or special occasions. Gold color adds classic shine to any outfit. This appears to be 18K gold but it could be 14K. The stamp on the jewelry clasp reads "PAT. D" (Patent Design) followed by a design patent number, which appears to be 77931 PAT. D: This stands for "Design Patent. : It signifies that the mechanical structure or visual style of the safety clasp mechanism itself was legally registered with the U.S. Patent and Trademark Office. • The Number: This unique patent registration number allows you to look up the exact date, mechanical blueprints, and inventor behind the mechanism. Design patents in this numerical range (50,000-80,000) typically date the creation of the clasp mechanism between the 1920s and 1930s. Clasp Style & ApplicationThe bracelet has a vintage fold-over safety clasp equipped with a figure-eight safety wire loop. This high-security mechanism is traditionally manufactured for luxury tennis bracelets and vintage watch bands to prevent the piece from accidentally slipping off the wrist if the primary latch pops open.