Featured 18k gold brooch

You are correct, but i'm in Panamá, don't take a risk. Just said to a wellknown person in that hotel: if somebody report a gold item lost, tell me description and i'll give it back.

 

Was hoping that was the case - too often people just choose the 'finders keepers, losers weepers' route...

It's a lovely piece, even with the slight damage.

~Cheryl

 

Yes, the hook is original, and where it should be. As evelyb pointed out, probably to attach a watch or other pendant.

I could probably go on for weeks showing you pictures of related headdresses and jewellery shapes from around the world. It is the combination of various details that is a clue in this case.
Nubian art has never had much influence outside northeast Africa.
Mucha was not influenced by ancient Egypt or any other African style. He was born in Moravia, a Slavonic region, now part of the Czech republic, and wanted to emphasize European tradition, especially that of the Slavonic/Slavic peoples of eastern Europe. This was the time of emerging nationalism.
Although the girl is called Byzantine, Byzantine headdresses were either higher up on the head, or embracing the face. Byzantine is probably a fantasy name, which could refer to the luxurious design and execution of the jewellery.
If you really want to find the origin of many Mucha designs, look at his passion and inspiration. For instance, the headband with temporal ring pendants is very prominent in Slavic tradition.
A Medieval Vyatichi Slavic girl:

Historic Polish headdress (Slavic):