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Continuity: When Manco is dealing the cards, the position of the cards dealt to Cavanaugh change over and over with each card dealt. A coin is visible on one card dealt, then it is gone on another deal. Manco's stack of cards he deals to himself also change from a neat pile to a slightly askew pile.
Revealing: After Monco beats up Cavanaugh and places Cavanaugh's back up against the bar, while Monco faces him, three of Cavanaugh's henchmen appear at the entrance of the bar demanding that Cavanaugh be released. Monco turns around and kills all of them with his pistol, while Cavanaugh falls to the floor crawling toward his gun. Monco is walking toward the entrance of the saloon with his back to Cavanaugh. Monco draws his gun and kills Cavanaugh without looking at him. If you look closely at the tip end of the pistol, you can see that the only thing that Monco would have killed was the saloon floor.
Revealing: About an hour and a half into the movie Clint Eastwood forces a telegraph guy to send a fake message saying the bank is being robbed, in a nearby town - as a ruse. In the next scene, when the posse rides down a dirt road, you can see tire tracks as they are all coming down a hill and going around a bend.
Other: 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.
Continuity: Near the beginning when Lee Van Cleef looks at the the wanted poster on the ticket booth at Tucumcari (just after getting off the train), there are two extra zero's drawn onto the poster (as added by the villain). Van Cleef then takes this poster away with him, and slots it under the door of a hotel room on a later scene - notice that the additional zero's have since disappeared from the same poster.






