Victorian Brooch Pendant Art Nouveau Green CatsEye

Beautiful sinuous lines on this Victorian era convertible brooch - pin to pendant piece. Stamped mark on the catch is M F & W. They are best known as a Cameo mfg. Pin is 7/8" wide and 3/4" tall. Gold metal with a wonderful patina. Plating and oxidation visible on the back, front excellent. Stone is green and is catching the light with movement typical to a cats eye or moonstone. Unknown exactly what it is, synthetic possible but don't know if they had that well done synthetic at that time period