Other mistake: About 20 minutes into the film, Tuco is arrested by the sheriff who rolls out a Wanted poster which has Tuco's picture. However, as can be seen (but only visible for a second or two), the name on the Wanted poster says Guy Calloway, who was a character in Leone's previous film For A Few Dollars More, who had a bounty on him (and a poster) and was killed by Col. Mortimer early in that film. Leone was notorious for trying to reuse props to save money (the Al Mulock story being the most infamous example), and possibly just reused the old poster with Wallach's picture on it, figuring nobody would notice. (00:21:03)
Other mistake: Blondie suffers from severe sun burn wounds in the face, after the capture and dragging through the desert. The wounds look perfectly realistic, but disappear or change several times. The burns are completely gone shortly after leaving the monastery. Such burns would leave scars and traces for at least weeks. (01:02:35 - 01:29:28)
Other mistake: In the very last scene of the movie, and just before Blondie shoots the rope that is holding Tuco on the grave's cross. You can see a car moving in the background, screen right of Tuco's head. (02:55:29)
Suggested correction: I've just watched this scene; there's no car visible. There's a bit where Blondie prepares his gun prior to aiming, then the camera switches back to Tuco. To the right of Tuco, in the background, a blurry something can be seen for maybe a second moving right to left. The object is far too blurry to identify. There's no reason to believe it's a car. It makes more sense that it's a horse-drawn wagon.
Other mistake: When Blondie and Tuco are talking about telling each other the location of the money, a car drives by in the background. In the shot where both Blondie and Tuco are visible, watch the top right in the trees in between the pillars supporting the bridge.
Other mistake: Director Sergio Leone uses one of his trademark filming techniques throughout this film, where anything outside the camera frame doesn't exist. Several times the characters react to situations and other characters when they come into frame that they logically would've seen much sooner. For example, at one point Blondie and Tuco are walking and stumble across an army camp. Even though in reality they would have been walking toward it for a long time and would have been aware of it, they react with surprise the moment it appears on screen.
