Iridescent Glass Cabachon With Mirrored Back Clip On Earrings, Silver-tone

So mysterious!!! I believe this is from a time circa 50s-60s, when glass artisans were trying to imitate Bohemian/Czech Dragon's Breath glass. Made with iridescent glass cabochons, back seems to be painted with mirroring silver. Metal does not react to a magnet, may be Sterling Silver, but seems lighter, and does not have that silver smell. The only marking says PAT PEND on the clip back. So what are they? A big iridescent glass cabochon for each ear hugged by a feather and a scalloped edge; and they're absolutely stunning!! Approx 1.20" x 0.80" x 0.33"