Grandma's celluloid brooch

This is a diamond shaped vintage brooch or cameo-style pin, featuring a figure accented with red and blue enamel. I'm not sure if the figure represents a male or a female. Is it Roman warrior figure? Medieval veiled lady? Nun in a wimple? Joan of Arc? No one knows for sure.

The cameo is set on a based which I think is celluloid, resembling ivory. This belonged to my grandmother, and probably dates prior to the 1930s. Grandma was born in 1902 and this pin could be much earlier than the 1920s, especially since Grandma and her entire family never threw anything away! I don't know the history of this piece, but it could have belonged to an older relative, as well.