The helicopter seen at the start of the movie is an American Bell 47. This did not enter US Military Service until 1946.
Major Von Happen’s uniform in the movie us one of an Allgemeine SS Officer. The use of this uniform was discontinued before 1944, and these Gestapo agents usually wore just plain clothes or a plain gray SS uniform.
The radio set in the movie that was used to communicate with the headquarters within England was just a low-power VHF transceiver. This only had a range of a couple of miles and did not have the capability of long distance transmissions.
General Carnaby could not have been going to Crete for his ‘rendezvous with the Russians’ as Crete was occupied by Germans and the Russians weren’t privy to any D-Day information – due to security reasons.
As Richard Burton walks across the square you see him saluting a soldier. This would not have happened as an Officer NEVER salutes anyone with a lower rank than himself.
As the coach travels through a village towards the end of the movie you see it move past a tracked vehicle. The vehicle in question is a Hotchkiss LPz; this was not manufactured until the 1960s.
Within the radio room of the castle, you see Lt. Schaffer sneak up on the German soldiers, and you witness soldiers changing the channel of the radio station. The music you hear playing is definitely not a style heard in the 1940’s and more like the 1960’s.
As the team of commandos is getting ready to jump from the cable car down into the river below, the ground view shows a naked road with trees at the side and German vehicles parked near them.
The view from the cable car of the same scene, however, shows a snowy road and no vehicles.
The official Where Eagles Dare Trailer: