It couldn't of been the Iron Mask episode, which was filmed on the same day as "The Two-Cornered Hat of Napoleon." Remember how they stood the Two-Cornered Hat on a red pot in the King's Storeroom? Well, the pots were red in the Little John Temple Run (credit to outer space for helping me find that out,) but "The Lost Lion Tail of Little John" was on a different production day, obviously the last one of the day before the Iron Mask production day.
Therefore "The Mask of the Man in the Iron Mask" could not have been 2x17. i had a hunch "The Missing Eye of David"'s day was first out of the layout, but i was going with Olmec and thinking "The Ivory Elephant of Scheherazade" would be 2x17.
This is all based on the King's Storeroom pot theory:
2x24 - The Lost Lion Tail of Little John
2x27 - The Mask of the Man in the Iron Mask
2x28 - The Two-Cornered Hat of Napol?on