Antique Cameo find at the pawnshop.

I ran across this at a local pawn shop. Much to my mothers good fortune. The back of the cameo appears to have acid etched initials in ascriptive style, possibly R M. I was struck by how the shell carving is very deep, almost to make the figure come off the background & appear more as a bust. The gold oval waves up & down, affixed to the inner ring by gold leaves & gemstones. The leaves are built in 2 levels, in alternating colours of gold (red & yellow), The amethysts are a deep purple which sometimes shine blue. I'd like to find out any additional info, especially about the carver. It could be L M or R M intertwined. I'm unsure.