the marking on back is trifari..? They look like ivory but are pretty light in weight?

I have a couple sets that has a "coro" stamp??

or does anyone know a good site where I can search this sort of thing? Find out more about jewelry stamps/markings? If something is of value ?

Illusionjewels.com has a great research site, and also links to more sites. They may be lucite or thermoplastic. Coro and Trifari did not use ivory in their costume jewelry.