Vintage Black Onyx Screw Back Earrings

Got these vintage screw back earrings with some nice black stones, looks like onyx or maybe glass. They're the old school screw-on type so you don't even need your ears pierced to wear 'em. The metal has a silver tone but I'm not sure if it's sterling or just plated. Cool little retro find for anyone into that mid-century look. They've got a bit of wear but still look pretty good for their age.