I think it is Navajo due to the amount of silver & the weight. Also the stone is sounded by a triangle setting that I see a lot in Navajo. It is also marked with letters, possibly initials which is more likely Navajo. not sure though???
I think it may be Kingman Turquoise because an engraving says: “Kingman Stamp”??? The turquoise is rough or natural appearing with silver like nuggets and what looks like gray stone almost cement gray in color.
It is marked with letters RD or I RD ???
It has the mark: TB 764 or T 13764???
I think it is antique???
Also how do I go about getting Native Jewelry Certified?