!!! PLEASE READ CAREFULLY IS A COSTUME NECKLACE !!! An authentic "MONET" stamp confirms this is an authentic piece of collectible vintage costume jewelry. Specifically, this is part of the "Estate by Monet" line, which specialized in creating elegant, premium-weight costume versions of luxury fine jewelry designs. Dating and Authentic Details * The Hallmark: If your necklace features a simple "MONET" block letter stamp on the clasp or tag alongside a copyright symbol (©), it denotes a production date anytime after 1955. This specific high-end, faux-gemstone style likely dates from Monet's late 20th-century collections. * The Setting: Monet was highly regarded for its triple-plating technique, which is why the silver-tone finish on your flat cuban/curb chain still retains a bright, mirror-like quality without typical metal corrosion or peeling.