On page 211 of WILLIAM SPRATLING AND THE MEXICAN SILVER RENAISSANCE by Penny Morrill is this Los Castillo treasure. I have wanted this necklace from the moment I saw it's picture. However I could not find one in superb condition until now. This is stated as being a difficult technique that was devised at Los Castillo. The onyx inlay is extraordinary and the look is sublime when worn. The weight is 110 grams with the center piece being 2in. x 1.25in. tall. The wearable is approximately 16in. It is correctly hallmarked as shown with design number 41, onyx negro eagle 15 los Castillo. Rare and perfect, just LOOK AT THAT NECKLACE!