Reply to Sah: I’ll jump in here with my two cents. I believe the cursive R hallmark on the back of your grandmother’s squash blossom is the hallmark of Sadie Randolph, a Navajo who began making jewelry about 1975, according to Barton Wright’s hallmark book. There is one website currently showing this hallmark belonging to “Sylver Ray Shop in Albuquerque” but I can’t find information on that shop. There was a Silver Ray jewelry store in Albuquerque but I can’t connect that information either.
If it was my piece, I’d pursue researching Sadie Randolph as the probable artist. Maybe others will chime in with better info.