Can someone tell me about this hallmark?

I hope the link for the image works. I believe the hallmark on the back of a necklace with turquoise says GTO. Can someone tell me more?

That is Q.T. with a copyright symbol for Quoc Turquoise Inc. in Alburquerque
I know they do a lot of native style jewelry, but have never gotten a satisfactory answer on whether or not they employ NA silversmiths, only that they employ NA “designers”. Maybe someone more knowledgable of the company can provide that answer for both of us.I have a pair of their earrings in a box here somewhere, they seem to be a popular brand.