There are pictures of his top side http://ball-pythons.net/forums/showt...79#post2262379 <--- There.
This guy came from craigslist, so it's entirely possible that at some point he had a horrid burn or belly rot or something, but there's nothing wrong with the scales or skin themselves NOW, and I have no idea if that would result in all the business on the lower half of his belly. The pictures aren't picking it up well, but the color on that part of his belly is also fairly yellow (as opposed to the white of his top half).
(For the record, I'm expecting to hear something like 'burn scar' or 'previous scale rot' more than a morph answer, or even just that some pastels do this. Still curious.)