Anachronisms: One of the gravestones near the "unknown" grave in the cemetery has the deceased dying in 1867, two years after the Civil War.
Anachronisms: Tuco examines a Belgian 10.4mm Galand revolver in the gun shop. The gun however was not invented until two years after the Civil War.
Continuity: Angel Eyes' grip on his spoon changes from overhand to underhand back to overhand while he chats with the rat.
Revealing mistakes: When the runaway Confederate carriage first appears in the desert you can see someone steering it. Then, as Tuco seizes the horse-team to stop the carriage, the reins are obviously being held by the out-of-frame driver. In the next shot, viewed from the driver's bench, the reins visibly tighten to halt the horses and then drop.
Anachronisms: While Tuco and Blondie are under the bridge, in the background where the poles form a 'V', a car passes through the trees. (widescreen edition)
Revealing mistakes: When Tuco and Blondie seek Angel-eyes in the deserted town, they discover a note that says "see you later idiots" but if you look closely at the paper, it is actually a page of the film script.
Continuity: Before the final gunfight, as Tuco is standing in the circle, he lowers his hand to the level of his pistol. His hand was already there in a previous shot.
Continuity: When Blondie and Tuco are carrying the explosives on the stretcher, at first the stretcher is missing several wooden slats, but as they approach the bridge, it changes into a completely different stretcher with no missing slats.
Continuity: Tuco has Blondie put his head through a noose and the way the rope is looped around the roof beam changes after the cannonball strike.
Anachronisms: In one scene, Tuco praises Lee and damns Grant out loud to the troops coming out of the desert. However, the movie takes place during Confederate invasion of New Mexico Territory in February- March of 1862, when both Lee and Grant were unknowns at this time. Lee didn't assume command of the Army of Northern Virginia until June 1862. Grant was a relative unknown when he won his first victory at Fort Donelson in February, 1862, hardly enough time for Tuco and Blondy to know who he was. That being said, in another scene, Angel Eyes mentions Confederate abuses in Andersonville Prison, which only became a prison and started accepting prisoners in February 1864.
Factual errors: When the two armies battle at the bridge, the Confederates are using the flag with the blue criss-cross on the red field. This is not the Confederate national flag, rather it is the banner of Gen. Robert E. Lee's Army of Northern Virginia. It would have been in battles in the east, not in the west.
Revealing mistakes: When Blondie says, "Your spurs," and shoots the last of the three ambushers in the hotel, the man falls backwards, knocking the wall and making it wobble.
Continuity: When Tuco and Blondie are carrying the crate with the explosives on the stretcher, it has turned about 90 degrees between the two shots when the music starts playing.
Crew or equipment visible: When the rhythmic music stops and Tuco is choking after screaming "Blondie", a person walking to the left can be seen on the left side of Tuco's face. You can also see a sun reflection on something carried by the person.
Continuity: Blondie and Tuco walk down the street of the desert town to confront the Angel Eyes' gang. At the beginning, their shadows are projected to behind them. Next shot, the shadows are projected in front of them.
Incorrectly regarded as goofs: Blondie's rifle is a Winchester, which was not available when the movie is meant to take place, but the production took the pains to remove the wood fore stock to disguise it as a Henry which were available.
Incorrectly regarded as goofs: During the bridge scene with the explosives, the fuse is often seen in the water. Would this mean it could not burn? No, because fuses were coated in wax, lots of mine & tunnel work back then occurred in damp & wet conditions.
Continuity: When Blondie is comforting the dying Rebel soldier near the end of the film, he gives him two puffs of his cheroot cigar - it changes length by almost an inch from shot to shot, first longer, then shorter, then longer again
Revealing mistakes: The scene is the one in which Tuco (Ugly) runs up to the carriage filled with dead bodies. When he opens the gate to the carriage and checks in, it can clearly be seen that the guy lying to the left is clearly blinking, even though everybody in the carriage except Bill Carson is supposed to be dead.
Continuity: When Blondie kicks the lid off of Arch Stanton's grave, the lid slides sideways along the ground. But, in the next shot, the lid almost hits Tuco in the face, like it was kicked upward.
Continuity: During the scene when Tuco confronts Blondie in the Saloon to hang him, he cocks the pistol twice.
Revealing mistakes: During the preparation of the charges on the bridge supports, they are connected in series, and Blondie lights only one (too short) fuse. When the bridge blows, all four charges detonate simultaneously, since they were detonated electrically.
Factual errors: In the US trailer (distributed on the DVD version of the film) the characters are misidentified. The character of Tuco is introduced as "The Bad", though in the movie he is introduced as "The Ugly." Likewise, the character of Angel Eyes is introduced as "The Ugly" (instead of "The Bad" as in the movie).
Anachronisms: When Angels Eyes first enters Stevens' house, an electrical tower can be seen in the background over his left shoulder.
Anachronisms: In the opening, when Eli Wallach is shown in close-up, he has an obvious cap or crown on a tooth.
Continuity: When Tuco enters the gun shop, he hangs the "CLOSED" sign at a downward-right angle on a nail on the back of the front door. As he exits the shop, the "CLOSED" sign is angled slightly down to the left.
Factual errors: If each gold coin had approximately 1 troy ounce of gold in it worth $20, $200,000 implies there were approximately 10,000 coins in the eight bags that Blondie and Tuco recovered. The weight of those 10,000 coins would be (10,000 coins * 1 ozt/coin * 31.1 g/ozt * 1 kg/1,000 g * 2.2 lbs/kg) = 684.2 lbs. Each bag would then weigh approximately 85.5 lbs. Blondie is seen loading up his horse with the gold two bags at a time (170 lbs). It doesn't seem likely that a person could lift that much gold without much more difficulty. Also, could a horse carry 340 lbs of gold, approximately 200 lbs of rider, and maybe another 50 lbs of provisions (roughly 600 lbs total load)?
Anachronisms: In the prison camp scene where the musicians are playing while Tuco is being beaten by Angle Eyes, the fiddle has fine tuning adjusters on the tail-piece. These fine tune adjusters were designed for metal strings used many decades later.
Anachronisms: A majority of the characters load metal cartridges into converted Civil War model revolvers. While this conversion did become commonplace in the late 1860's, back in 1862 metal cartridges hadn't been fully developed for those kinds of revolvers yet and paper cartridges were still the norm.
Anachronisms: During the course of the movie, people are shown loading bullets into black-powder pistols. Bullets were not used in pistols at that time.
Factual errors: At the end of the movie Blondie flips up the long-range leaf sight on his rifle but the cross member is so loose it falls down to the very bottom. This would give him no elevation of the gun barrel to allow for bullet drop, at the 1000 yards he must have been at, to make that shot.
Audio/visual unsynchronized: During Tuco's beating in the POW camp, one of the fiddlers stops playing. The singers behind him are still singing but only the music is heard.
Continuity: Near the end of the film, when Tuco's head is in the noose in the cemetery, the tightness of the knot keeps changing between front and rear shots.
Revealing mistakes: Leading up to the final gunfight, there are several close ups of Angel Eyes' hand creeping toward his gun. The gun is clearly a Remington percussion type, but there are cartridges visible on his gun belt.
Incorrectly regarded as goofs: When Tuco and and Blondie ride their coach up to the mission to recuperate from the desert several power poles are visible in the background to the left. (May only be visible in the wide-screen version). However, one can make the assumption that these are telegraph lines since the telegraph was a common form of long-distance communication during the civil war. Power poles are even visible by the train tracks when Tuco escapes his captive. Which makes sense since telegraph lines were commonly built along railroads.
Anachronisms: Tuco and Blondie blow the bridge using dynamite, which was not available at the time of the civil war (1867 onwards).
Continuity: One of the three bounty hunters that shoots Tuco off his horse has a piece of grass in his mouth just prior to been shot by Blondie, that was not there in the previous frames when he tells Tuco he has a face worth 1000 dollars.
Continuity: In the deserted town, Blondie hears Tuco's pistol as he shoots the one-armed bounty hunter and says "every gun makes its own tune." But Tuco had been captured by Union cavalry, held in a prisoner of war camp, and was being transported for execution, and would presumably not be allowed to retain his handgun. Cpl Wallace, the brutal guard, also doesn't have the gun when they exit the train - Tuco's gun has a ring on the handle he used for a cord. When Tuco tried to use Wallace's gun to break the chain attaching him to Wallace's corpse, it clearly doesn't have a ring, and Tuco tosses it aside. From Blondie's words, we know it's not a similar gun - it must be the SAME gun, since it makes "its own tune." The gun Tuco has in the deserted town has the ring again.