Hey Brian.
I always wondered about that myself. I watched the movie, and I recall that all of the uniforms looked correct.
I remember one scene where they were clowning around in the barracks with a real pickelhaube and some guy brought his rear rear end down on the spike to much hilarity. All of the pickelhauben looked real to me, but they were probably everywhere right after the war.
The uniforms looked good, but from what I have heard the old studios back then had armies of cheap seamstresses sewing and working costumes off set, so you never know if a screen used uniform in black and white might be the real thing. They are easy to spot in hand though, if you know what you are looking at!
I do remember a scene where they showed a big attack across no man's land, and a German bunker was shown from the front firing away with a machine gun. It was obviously a Vickers Mk1 variant with a blank firing device, and it looked like they didn't have it on a tripod. Just balanced the end of the water jacket on the edge of the sandbags in the firing slit of the bunker and waved it around while firing blanks for dramatic effect I guess. Couple of "Germans" in it with M1916 helmets...
One thing I remember asking my buddy back in California was about the WWII German uniforms used in the TV show "Combat!" and other older movies and TV shows, and why the color seemed off from the real thing. Almost a purple-ish and gray hue to the cloth. A really goofy color.
He told me that back in the days when everything was in black and white, and lighting and background were important, colors for studio-made clothing and uniforms were important in order for the audience to see them stand out properly in the film shot.
I think that is why you see a lot of goofy colored uniforms worn by German soldiers in the movies in the late 60s and early 70s. The studios had not bothered to change over for color film yet.
I have several of the old style studio goofy colored German uniforms at my house in California. If I remember, I will photograph a couple and post them in December when I go back out that way to visit.
Bryan.