1/20 12KGF and then an "H" in an elongated diamond

by Nicole medina
(Plantation, FL Broward County)

I have a deco looking gold filled brooch with pearls and a mark that says
"1/20 12KGF" and then an elongated diamond beneath with an "H" inside. I can't find any information on this mark. I am attaching photos for your consideration. Thank you