During the fencing duel between Dantes and Mondego, in one brief shot near the end Sidney Blackmer holds his sword in his left hand instead of his right, which he does in the rest of the scene. This was obviously a shown in reverse as is often done to add footage.
Edmond Dantes tells Abbe Faria that he has been imprisoned since February 28, 1815. Just before the Battle of Waterloo on June 18, 1815, the full-screen shot of Dantes' s supposed Death Certificate shows its date as March 15, 1824.