Antique Cameo pin/pendant

 This was part of an estate sale that my mother put on and it didn't sell. It's been in it's box in the basement and is in good condition albeit a bit dirty. Nicely carved out of shell, has no visible markings, no visible cracks, c clasp makes me think it pre-1900(guessing). No idea of metal of frame, possible brass From research possible Athena, with second face carved in the helmet.