I believe the numbers and letters following the star on the clasp will identify who made the piece, but I don’t know where to find a list of “makers” - and truthfully, that information isn’t likely to affect the valuation of your necklace. If you want to explore this on your own though you might poke around 925-1000.com. It’s a site for silver enthusiasts, but I’m sure many jewelers made both gold and silver jewelry so the information might be transferable. (Or not. It’s also possible that jewelers had different id numbers for their work in different metals.)
