You're wrong. :) It's an overo. Tuffy is what most people call a frame overo but if you get really technical, he's a cross between an overo and a sabino. Overo's typically don't have white legs and Tuffy does.
Kinda funny to see you posting through 100 posts behind ;~D See you in a few minutes when you catch up :~D
Lordy! I'm dealing with a bunch of amateurs here! :)
There are actually three distinct color patterns which are being lumped together under the overo name. These three patternsare frame overos, sabiano overos and splashed white overos. Each of these patters is genetically different and distinct from one another. Each of these three different overo patterns consistently place and characterize the white. Each of these three different overo patterns is dominent. In the past these were throught to have been recessive and there was some confusion mainly because all three of these patterns were lumped under the same name "overo" when in fact each is a distinct color pattern.
Since the topic of discussion was on frame overo, I'll limit the rest of my comments to that pattern. The frame overo pattern is a dominent allele. In some instances, the frame overo allele may appear to be passed as a recessive allele, but usually due to a minimally marked animal non having any body spots. Cropout horses may imply that there is more than one allele involved, and it may be more complex. These cropout horses do reproduce this frame overo pattern as though the gene were dominant. This suggests that cropout horses may be due to new mutations of this allele.
The frame overo horse may have minimal white to extensive white markings. Horses which have been classified as solid breeding stock horses may be a minimal white frame overo without any body spots, dark legs and extensive white markings on their face, such as a bald face. These horses are expressing the minimum of the frame overo color pattern. The tip-off is usually the combination of abundant facial white with minimal leg white. These horses do not have any body spots, but do produce foals with spots.
The frame overo allele can be responsible for the production of lethal white foals, which die within 48 hours of birth, usually. It has been thought that the lethal white foals are homozygous and have recieved a frame overo from each parent. This may be more complicated because solid horses (by a frame overo parent) crossed with a frame overo have produced lethal white foals.
Hopes this helps!