So what is going on genetically in this piebald cob?

What do you mean by "merled"?

Sorry Chiilaa, I think it is more of an American term, but it describes a broken blue/black coat in a Boder Collie or an Aus. Shepherd dog (or red/brown merle.)
Like this- blue merle - Google Search

And many people use the term "merle" (however correct or not) to describe horse eyes that are part one color (like blue) and part another color (amber or brown) but within the same eye.
I know there are some other common names for this, but for the life of me, I couldn't think of any.

That's what I thought it was, but just wanted to check before I assumed lol.

It's still probably caused by one of those two genes, but there may be something else going on that we don't know about yet. It could be that white suppression genes also try to keep eyes brown, it could also be that other genes actively try to do it.

Ok, Thanks.
I'm thoroughly confused now by my horses eyes, but don't want to hijack here. One of these days I will post his eyes in a thread to see what people think. I'll be sure to bug you to take a look too.

Handsome cob. He's tobiano, splash and possibly some type of sabino. I doubt seriously frame, since there are so few horses in the entire UK, which carry it. He's probably got Gypsy cob in his background somewhere and frame has never yet been found in the breed. Does he ever grow feather? Another clue, is that Gypsies love to jump.

Lizzie

Parti-color? Sectoral heterochromia (which I have lol)? I've only ever heard of the word "merle" associated with coat color in dogs mostly.

I'm no help, but he's gorgeous... love your sisters show jacket too!

He does grow some feather, although overly much - comparable feather to a Welsh cob I guess. Not nearly as much as my friend's Irish cob, who looks like a 14.2hh Shire! But he is a cracking jumper, absolutely loves it (:

I'm very technomalogical with my breeding and genetics terms - this horse clearly has the Stunning gene, and is probably from the Bovis line and with a high percentage of Ohmygodithinkimightstealhimoffyou.