Other mistake: In the first scene at Marseilles, the shipping company's sign reads "Morell & Co. Shipping", but the owner's name is spelled "Morrel". French spelling didn't vary at the time, since the French Academy had by then been in place for some 200 years. And even if a businessman might not spell everything correctly every time, he would at least know how to spell his own name right and would make sure it is so on such a commercial sign.
Other mistake: After the knife fight and the Captain giving Edmond the name Zatarra, the scene cuts to the ship entering a port and the words "three months later" are shown on the screen. By the movie timeline it should have said "Three Years Later." (01:05:20)
Character mistake: After Edmond changes his identity to become the Count of Monte Cristo, he is addressed several times as "Your Grace." "Your Grace" is a term of address used when addressing dukes and duchesses. He should have been addressed as "Your Excellency", which is the address given to counts and countesses.
Continuity mistake: When Edmond Dantes is being swung back and forth to be thrown over the cliff the seams of the body bag are on top. However they show him looking through the seam as the bag is swinging as if the seam is on the side. He would have only possibly been able to see at the furthest point away from the keys yet the view of the keys is clear as the bag is swinging closest to the keys. On top of this the angle of the view of the keys would mean his head would have to be in the middle of the bag to be lined up with the keys. In the next shot his hand is lined up with the keys.robsuttonjr