Lance black tank area access panel?

Good find, I guess Im just missing the door, it's definitely on that unit.

I'm unfamiliar with Lance construction- hopefully some one will chime in but if its a contained/closed compartment cant image it should be open to elements.
I cut out back side but for access when I rebuilt skirt, and replaced with cutout. That area can see a lot of road wash?

edit looking around several photos 2012 and others show but all have solid panel not open hole
https://www.youtube.com/watch?v=hX2ir9MtGN8 just one