Vintage Fred Harvey Era Thunderbird Turquoise Screw Back Earrings Sterling?

Vintage Southwestern Thunderbird screw-back earrings featuring turquoise cabochon centers. Estate-found examples believed to date to the Fred Harvey era (circa 1930s-1940s). No sterling mark found; metal untested. Please review photos and judge age, material, and attribution for yourself. Jesus Loves You! ❤️