Two Gray Hills? wool Navajo? rug

I found this rug at a yard sale in Denver Co. I believe it is a Navajo wool rug / textile and after researching a bit on line think it may be a Two Gray Hills rug. I was curious first if it is in fact a real Navajo textile and also if there was any way to roughly date the rug. In one of the corners it has what I think is called a "spirit line" . Any information first if it is authentic and if it is a Two Gray Hills and lastly a way to help date the rug. Any help would be appreciated.