Value??

I have a shadowbox necklace from my late Mom and trying to sell. I also had a squash blossom necklace that I sold and took a beating on because after I sold it I had bids for twice the price. Don’t want to do that again but not sure of the value of the piece. How do I find out? Also it has initials scratched into the back of the medallion part of the necklace G.O.

Marilyn, welcome to the forum! A photo, front and back, in natural light will help us figure out what you might have!