Sheriff Russell is an homage to Bing Russell, who played Deputy Clem Foster on Bonanza (1959) (and was the father of Kurt Russell).
The real Frank James never lived in Nevada, and was no longer a wanted man after he surrendered to the Governor of Missouri in 1882. He lived to age seventy-two and died in Missouri in 1915.
A Mauser type semi-automatic pistol, possible a Model C96, is seen in this movie. The Mauser C96 was manufactured from 1896-1937. It is interesting to see this more modern looking technology in the old west as they are more commonly seen in WW1 and WW2 movies. It could be seen as symbolic of the rapidly changing times at the turn of the century.
Dirk Blocker, who played Fenster, is the son of original Bonanza member Dan Blocker who was Hoss.