Factual error: On the night of 19 October 1933 the railroad workers begin betting whether A-One will make it to Portland on the 19. A quick closeup of the money changing hands reveals the $1's to have the Great Seal reverse (introduced in 1935) plus the motto IN GOD WE TRUST (introduced in 1957). Also, the green-seal Federal Reserve Notes and the red-seal United States $2 notes are of the types first introduced in 1934.
Factual error: While Sgt Howie (dressed as Punch) is being chased by the women, you can see autumn leaves on the grass, though the story is set on the 1st of May.
Factual error: When Clint Eastwood first goes to the barber shop, the barber very deliberately sharpens his razor the wrong way, flipping the blade with its sharp edge against the strop - this would instantly dull the blade. No real barber would make this mistake, but it's a common movie error.
Factual error: In the scene where Kananga's henchman, Adam, is being interrogated by Sheriff Pepper by his car at the riverside, the boat chase arrives and two boats jump clearly overhead, disillusioning Sheriff Pepper and allowing Adam to make a quick getaway. However, as Adam is getting away in his car, screeches can be heard coming from the tyres, but they are on a dry dirt road.
Factual error: Many shots, especially the early ones, include the iconic Renault 16 in the background. This car was first produced in c1965, three years after the events happened. Probably unavoidable, as the car was a huge success.
Factual error: The kid is wearing a Texas Rangers baseball cap. The Rangers didn't come to Texas until 1972.
Factual error: During the flashback explaining what happened to Su Lin she has an ugly bruise on her face less than a minute after being hit. Bruises usually take at least a few hours to develop like that.
Factual error: The woman walking past waiting fares, saying "excuse me, this is important." She gets into the right rear door of a 1963 Chevrolet, with flat door sill. In the interior of the car there is "Kick Up" in the doorsill, and a Ford door release handle, flush with the side trim. The 63 Chevy had different handles.