This is an old cameo has a c-clasp on it.  Long over hanging pin.  That was sort of the traditional pin from about 1850 to just about the turn of the century.  Condition is quite good considering its age. Has a couple stress lines. This is normal and to be expected. Does not effect integrity of the shell The frame/bezel is unmarked. If I were to guess I would say it is brass. Although it is in super great shape no tarnish at all. The shell is dark in color. The profile raised and ivory color, great antiquing on this really brings out the detail. As far as who this is? We are not sure educated guess might be Diana the huntress or maybe Selene the moon goddess. Comes in a velvet box.