Not very attractive, sadly.
It looks like it's suffering from some sort of skin complaint.
If it were reversed it wouldn't cause comment would it.
So, what do the colour experts say then?
I believe it has an auto immune disease called alopecia aerata. Initially there is hair loss, generally starting on the face. When the animal is treated and the hair grows back in it usually has turned grey.
<span style="colorurple">I asked on another [mostly American] MB and they think it's probably a warmblood or sport horse derived from an appaloosa crossed to something else... </span>
someone from the other MB managed to email the owner and asked, she says he's a Hanoverian x TB and has a genetic "thing" that she can't remember the name of that's causing the strange markings... he was originally bay with a star and sock