The few I've seen were marked GR Douglas. I may be mistaken, but if I remember right, some of the Hawken style rifles they made had them. Others I'm sure were added by owners.
My GGGGG Grandfather John Young was appointed by Colonel George Clendenin as a spy in April 1788. He had served as a teenage rifleman in the Revolution and moved to the Kanawha Valley in 1783. He married Lewis Tackett's daughter Keziah in May of 1789 and on October 5 of that year was named one of two lieutenants in the first government of Kanawha County. His first born, my GGGG Grandfather was the first white child recorded as being born in Kanawha. The next day Tackett's Fort was attacked and burned with several killed and captured and John with his wife and baby escaped to Ft. Lee. Later Young and Tackett bought the first two town lots in what is now Charleston and Young was one of the first trustees. In 1791, he was under the command of Daniel Boone who made his home in the what is now known as Kanawha City section. Boone listed him as being in command at Elk River with 17 men.
My muzzleloading group's range is just about 3 miles south of the site of Tackett's Fort on Coal River.
Who knows? We may be kin. There were several other Rangers who worked with Grandaddy. His brothers, Fleming Cobbs and the Morris boys to name a few.