It might be hard to find out exactly what era jewelry is from, since there is so much reproduction stuff floating around.
Look for hallmarks (stamps on jewelry that indicate metal, and manufacturer). If you find some you should be able to look up the hallmark to find out who made the jewelry and when they made that style.
I think it would probably be safer to re-assemble the jewelry and call it handmade. That way you're sure you're not marking something as vintage when it might not be. Unless you think the jewelry might be really valuable as it is, that might be the way to go.
Otherwise it might turn out to be a guessing game.