925 Sterling Silver Single Opal Earring By EFFY (?)

Classic stud earring with a shimmering fire opal centerpiece. Single earring, suitable for a third hole, or an asymmetric look. The back is stamped 925 EFFY. The earring post is not stamped, so I don't know what the metal is. The opal stone is natural and has good fire. It has a tiny surface hairline, which I can't capture on camera, and also one small imperfection on the edge (last picture, bottom right).