Other mistake: At the beginning of the film, you see Colonel Mortimer traveling on a train while reading a bible. He has a Indian squaw and a gentleman wearing glasses and a derby sitting across from him. A conductor comes by to pick up their tickets. Colonel Mortimer asks the conductor, "is it far to Tucamcari?" The conductor replies, "we pass there in three to four minutes." The gentleman with glasses starts to tell the Colonel that he is on the wrong train. As he tells him this, look out the train window and see a car driving off into the distance. (00:04:30)
Other mistake: The man with no name goes through roof to get the money. The director put him in blackface to darken his skin so to only focus on his eyes and mouth. Not a very good job. You will see leading up to the roof and when he jumps down from the rafter to encounter the Col. Douglas Mortimer, his face is clear of makeup. I guess it was the best they could do to get the lighting they wanted during the scene.
Other mistake: After they shoot each other's hats and are in the hotel room, Monco says who goes around with a contraption like that (referring to Mortimer's gun). Mortimer says that contraption almost sent you to your grave. In the heat shooting scene Mortimer uses a regular pistol, not the contraption.