This is a RARE vintage necklace. The necklace is hallmarked with the name Diaz Santoyo and the intials CJB. This hallmark is listed in "The Little Book of Mexican Silver Hallmarks" on page 163. The hallmark also contains, "Hecho en Mexico" and Plata 925. The necklace measures 18 inches long and has a simple loop and hook clasp. The green onyx stone has been beautifully carved and polished and surrounded with twisted silver wire and silver beads. Most of the necklaces like this one are in black onyx, this is the first one I have had in the green onyx. It is in excellent condition. See pictures for more detail.