Although the film is set in 1956 Hungary. The opening title of the movie is The Austrian-Hungarian Border 1960.
At the beginning of the movie where some refugees are delivered through the Austrian-Hungarian border by a hay-cart it would seem that a border is only a wire fence with wood made watch towers and a very simple gate. In fact there was the "Iron curtain". It were two strong fences with a distance of ca. 25 meter, between the fences was made a mine field. The first fence (Hungarian side) had an alarm system (if somebody touched the fence it made a signal for the border police), a second fence (Austrian side was an electric fence. Cca. 2000 m after the second fence was the real border line. So it wasn't possible to go through the border like it was shown in the movie.
The "Count", who wanted to rescue "Jancsi" and "Reynolds" from the prison arrived with a big car. Normally a major-rank officer in State Protection Authority didn't have legitimacy for a ZIS-110 or ZIL-110, but only for a GAZ-M-20 Pobeda. The second thing, that a ZIS or ZIL never had such a cooler grill ornament which is visible in the movie. The soviet car had a red flag form plastic ornament, with a star. So the car in the movie is an American Packard 180 with a swan ornament. Such car never was in Hungary.
The street signs and the house numbers are Austrian types, not Hungarians.
The State Protection Authority or the police didn't have Wartburg 311 cars as service car... They had either Pobeda (GAZ-M-20), or Moskwich 407, but only Russian (Soviet) made cars.
Right before the escape by the plane is a road sign visible "MÁTYÁSFÖLD". Yes, there was an airfield, but since the Revolution in 1956 it was occupied by the Soviet Army , and was used as military airfield. So it wasn't an International Airport. And it never has concrete runway. The only international airport Budapest is about 25 km far from Mátyásföld.
All people in Hungary are speaking well English in the movie, but poor Hungarian. Officers in the border police, or policemen didn't speak English because it was fishy and criminal in Hungary in the 50-60's.