Made in Mexico Mexican Sterling Silver Amethyst Poison Ring - Adjustable 6

Dating to the 1950s/1960s or so, here's a Made in Mexico Mexican Sterling Silver (hallmarked as pictured) poison ring. Featuring an amethyst cab to the top that is completely natural with color differentiations (medium with an oval patch of light) and inclusions within the gem, the ring is adjustable and currently measures a 6 on my sizer. Height of the ring from the shank is about 5/8"; design on top measures 1" north/south x 3/4". Weight is 9.6 grams. As you can see, there is a lot of tarnish on the piece - a light polish will bring up a high shine. Lid opens easily and closes securely; it doesn't open very far but enough to slip in what have you. Getting harder and hard to find!