Nope, it's not an extra door key. I have two keys for the door and one key for the outside shower. That leaves me with two extra keys that are identical. The mystery keys only have one notch in them along the part that you insert into the lock, so I'm thinking that it must lock some type of basic panel just to keep kids out or something that doesn't really need to be secured that well. I just haven't been able to find what it goes to.
I am going out for the maiden voyage next week. I just graduated from tent camping so I am busy reading the manual and getting the camper filled with the necessary items.
I can't wait though!