Carved Cameo Gold Filled Brooch Pin Vintage Pink Shell Engraved

Beautiful carved shell cameo brooch is a lovely lady in profile mounted in an engraved gold metal frame. I don't see a content mark, but it looks like it's probably gold filled, and the frame is decorated with little foliate designs. The back has a safety catch with what looks like a maker's mark, possibly a letter N or letter E, I just can't tell. Looks wonderful but the back has some discoloration of the metal, some finish wear and one small greenish spot near the bottom. Front looks great, very pretty with the varied shell colors on pale pink background shell. 1 1/2" x 1 1/4".