Material: K18 (18 karat gold) The ball chain was stored for a long time with almost no use. The onyx was used frequently and then stored for a long time. Purchased at Shinjuku Mitsukoshi. The hallmark is from the Japan Mint (a Japanese flag and a diamond shape indicating the purity percentage). The onyx top has been used. The engraving here is only K18. I remember purchasing it at a jewelry store in Shinjuku Lumine. Decoration: Onyx