Factual error: John Wayne and James Caan are in the gunsmiths shop, and behind the gunsmith on the shelf are some products, one of these products is Bugler tobacco. Bugler tobacco was introduced in the United States in 1932. (01:00:00 - 01:02:00)
Factual error: In the scene near the end of the film where Victor Buono is sitting in his chamber addressing his two captives, he opens a can labeled egg foo young with a can opener. He pours the liquid contents into a bowl. Egg foo young is an omelet and could not have passed through the small holes made with a can opener.
Factual error: The British carry WW-I, No 1 Lee-Enfields, and the Germans carry WW-II era British No. 4 Lee-Enfields.
Factual error: In the scene where Lee Marvin states that Burt Lancaster loves explosions, Burt Lancaster makes a remark about the big bang theory. He says: the whole universe started with a big explosion. The film is set in 1917 which is 10 years before Georges Lemaître launched the big bang theory.
Factual error: Racer Dave Owens goes down to an unspecified Southern state to race and becomes a moonshine runner. However, the Dodge he drives in his illicit activities possesses California plates, as does the Plymouth driven by the IRS agents.
Factual error: When Tuco is in the gunshop messing around with the guns, one gun has the cylinder and barrel moving back and forth by manipulating the trigger guard-lever. This is a Belgian Galand & Somerville revolver, a gun that did not exist until 1868. This film takes place during the US Civil War, which ended in 1865.
Factual error: When Riddler's rocket hits the Batcopter, the villains are watching from the periscope as Batman and Robin are crashing. However, the image they see is a straight-on shot, as if the lens were right in front of the copter. No pre-atomic periscope can reach that far up.