Antique arts and crafts, medieval revival, Byzantine Revival white enamel, faux topaz discount after Rikers and sons stickpin

Arts and Crafts movement stickpin, after the designs of Riker and sons of New York, white enamel with lines and circles with a discount floating faux topaz cabochon in the middle. It is designed after the Byzantine revival movement of the arts and crafts. It measures 2 1/2 inches long. Thanks for looking!