Vintage Mexican Silver pendant with matching earrings

Vintage Mexican Silver pendant for necklace (chain not included) with matching stud earrings. Marked on the back of both earrings and the pendant itself. Unsure what kind of stone this is or the original place of purchase. Was given to me from a friend who didn’t know the history of this set of jewerly either. Price is negotiable. Hasn’t been professionally tested to prove the marking is because it’s real and not a fake.