Other mistake: When they are lifting the boxes of gold at the end of the movie you can tell that the boxes are empty.
Other mistake: When Telly Savalas drives into the farmhouse he leaves the chaplain in the jeep which is approx. 50 feet from where Clint Eastwood and the rest of the soldiers are planning to steal the gold. For about five minutes they are arguing quite loudly about if it is a good idea and afterwards they then agree to the heist and they all crowd around the map and are extremely jubilant. Is the chaplain still sitting in the jeep listening to all this? We never see him again.