This is a vintage 12K gold filled black onyx choker necklace and matching screwback earrings. The necklace is simply marked 12KGF but the earrings are marked B-M Co., 12KGF. B-M Co. stands for Bauman-Massa Jewelry Co. of St. Louis, Missouri and the mark was first used in 1889. The necklace measures 15 inches long and the center drop measures 1-1/2 inches long. The screwback earrings measure 1-1/8 inches long. The set is in very good condition and appears to be gently worn, if at all. Please let me know if you have any questions. Thanks for stopping by.