It's surprising how many big budget films contain errors of this kind.
Most were fleeting, such as the red sports car from Ben Hur (better still, one of the trumpet players at the start of the race is seen wearing a wristwatch ), but were left in, I suppose, because the filmmakers did not consider the audience of the day to be that observant.
Did you also happen to notice that in one scene the explosives were revealed by the drop in the level of the river, yet when Sir Alec falls on the plunger and blows the bridge the explosives are now at the level of the bridge deck ?
Mark Lee