This is a necklace my grandmother kept for many years. It seems she used it occasionally. The metal parts are 18K gold. There is a hallmark on the clasp. Please refrain from purchasing if you are concerned, as it is not the Japan Mint's hallmark. The black parts are likely black onyx, but as there is no way to confirm, the material of the black parts will be treated as unknown. If you have any methods you would like me to check, I will do my best to accommodate you, so please let me know. (I cannot disassemble the parts.) The cut is beautiful. Not only round, but large hexagonal parts are used extensively. If you look closely, the hexagonal parts are arranged symmetrically in the center of the necklace. The total weight of the necklace was 12.73g on a household precision scale. The front is double-layered, giving it volume despite its slender design. It has a simple yet sophisticated design. While single-strand, rosary-like necklaces are common, I think this design is quite unique. The 18K gold fan-shaped parts at the transition between the single and double strands sparkle and reflect light, making it look cool. The length from end to end of the clasp is approximately 43 centimeters. There are areas on the surface where the reddish tint characteristic of 18K gold has deepened slightly, but please understand this as part of the aging process. As it is not plated, there is no rust, peeling, or discoloration typical of plating. I would like to give this to someone who will not resell it. I would be happy if I could pass it on to someone who will cherish it. Vintage, Showa retro, antique, 18K gold, k18, 18k