I like your cameo very much! With the wisp of hair falling at the nape of the neck, she is so divinely feminine; there is such an energy you can sense when you look at this cameo lovely. It looks Italian Amiar. No mention of the metal composition of the frame?
The shell looks to be Cornelian which is the most common shell used for Cameo carving, although you mentioned it has a brownish tint, which suggests Sardonyx shell. Sardonyx shells are liked because of their unusual colour pigmentation. Sardonyx has a pure white mid layer and a beautiful deep red to chocolate brown interior.
Because Cornelian has less white colouring between the layers, the carved profile will not be as white as the Sardonyx profile. This is the reason I lean towards Cornelian Shell as the shell material of your cameo.
