Turquoise ring R Hallmark

Hey there. This piece has an R hallmark and maybe what looks like a 6 on the other end of the ring. I have looked in the Hougart hallmark book and at the online resource Amerindien Hallmarks but am unable to find a hallmark that looks like this. Any ideas about this script hallmark, who it might belong to? Guessing Navajo artist.

Also maybe ideas on the type of turquoise?

Thank you.