Either this is from the 20's or a very old reproduction - definitely not of the last few years and high quality. Stamped something that may be 925 or STF (sterling, France? - looks French), it is heavy sterling with all of the tiny marcasites intact. Don't know if black is glass or onyx but it is in perfect condition too. Those are cutout triangles in the center as are curved sides. Measure 1 7/8 x 1 3/8 - excellent condition. Some faint marks may be the artist.