Mexican Sterling Silver and Green Obsidian Locket Pendant Pin

Vintage Mexican sterling silver pin / pendant set with green obsidian Cage setting. Hallmarked on the back. Locking clasp with bail for a chain at the top. The obsidian has a chip on the side. Hinged door snaps down tight. Pendant measures 1 3/8" by 1 1/8". Weight: 18.7 grams. Very tarnished and needs cleaning.