Other mistake: Labiche uses binoculars to view the coupling of the armament train from the control tower (when they are deliberately delaying train coupling), but the binoculars are in the closed/stored position, lenses close together. You cannot view through them like this as they don't line up with your eyes. In a later scene, when Papa Boule is driving the train through an air raid, he uses the binoculars correctly in the open position.
Other mistake: When Papa Boule kicks Labiche off his train and tells him to throw the switch (turnout) Labiche actually operates one behind the train, not in front of it.
Answer: In several location throughout France, from Paris to Mertz, with many scenes being filmed on location. You can find more details on IMDB or Wikipedia.
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