I looked up the Monaco when you were asking about the model earlier and saw that they were indeed aluminum. I had thought only Lazy Days were aluminum.
I didn't realize metal oxidized, but I guess the paint itself could. The contrast looks too dark to be Zep floor finish but a simple wipe with ammonia would tell you if it comes off like that wax does. Otherwise it seems more likely that it would be the paint itself--or clear coat as someone mentioned.
The screws/rivets along the side look different from fiberglass siding which on my rig the fiberglass is secured at the trim pieces.
Seems like you could try a few removers in a small area away from the graphics which look really good for a 2003, and see if any of them whiten the surface.
It also looks like there are gaps on your trim where the dark areas are in the photos that may need caulk.