Near the end of the film, when Zorro is fighting Don Raphael Montero's American henchman Capt. Harrison Love at the gold-mine, we see a shot of the boiler that Captain Love has sabotaged in order to blow up the gold-mine and the slave held captive there. To show how perilously close the boiler is to exploding, there is a shot of the pressure gauge on the boiler with the dial in the red. The slip up is that the gauge is showing Kg per cm2, when the metric system hadn't yet been invented. It should really have shown lb per square inch (psi).