Black Glass Cameo with an Engraved Star Mark

by Tanjla
(Colorado)

Here are some photos of this black glass cameo that I can find no information on. It appears to be glass and has a c-clasp. There is a star engraved in the back of the cameo.
Can you tell me anything about it? or the maker? Could it be French Jet?

Thank you,
Tanjla