Visible crew/equipment: The shadows of the camera, crew, and film equipment are visible several times in the sequence when Clint is riding into the Native American camp and the two men are buried up to their heads. The equipment is most visible in the scenes when the sun is facing the Native Americans.
Visible crew/equipment: Just as Sondra Locke is about to have her shirt ripped off by the Comancheros you can see at the top of the sand-dune/hill behind the men, (in the background), a yellow digger. (01:19:27)
Factual error: In the beginning when seen the Union attacking, the American flag has 50 stars not the 36 at the time of the war. The flag is incorrect.
Suggested correction: First, it's not a 50-star flag. There's a clear shot of the flag in one scene where you see it has 3 rows of 7-stars and 2 rows of 6-stars for 33-stars, although not in a pattern I'm familiar with. There's another shot where it's less clear, but you still only see 5 rows of stars and not 9 offset rows. Second, Nevada was the 36th state and didn't join until October 1864. The 36-star flag wouldn't have come out until July 4th, 1865, which was after the Civil War and wouldn't have been flown during the war.