Tiffany & Co Vintage Sterling Silver & Black Onyx 30.5 Inch Single Strand Beads On Chain Necklace. This stunning necklace has a small round tag that is engraved: TIFFANY & CO 925. It weighs 79.4 grams. The large onyx beads measure 10.2 mm round and the sterling silver beads measure 6 mm round. It has been beautifully cared for and is in excellent to mint condition. It comes in it's Tiffany pouch and box. Please visit my ebay store for fine estate jewelry. Thank you.