Vintage Teardrop Shaped Turquoise Ring in Sterling Silver Size 9

Vintage sterling silver ring in a teardrop shape. It is set with a large medium turquoise stone that appears to be natural.  It is hallmarked on the back. This mark may be Navajo but may also be Mexican. Face measures 1 1/4" by 1". Weight: 10.8 grams. Great condition. Rustic.