Factual error: Proteus refills its air supply in the lungs. The lungs are filled with normal sized oxygen molecules. How are they supposed to breathe them? (In the book, they had a miniaturizer on the sub, but there is nothing in the movie to explain this.)
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: The British carry WW-I, No 1 Lee-Enfields, and the Germans carry WW-II era British No. 4 Lee-Enfields.
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.