This is a wonderful Art Deco monogram hanging brooch in silver with marcasite intials "FS" against what looks to be a black onyx or jade background. Really a lovely piece for someone with these intials. I have not had the silver tested, but it looks to be solid silver. Condition is wonderful. Circa 1925. Most likely French or German in origin. Is your name Felicity, Fiona, Francine?? This brooch is for you!