Model Horse Blab is an excellent place to get information, and often what I read sends me speeding upstairs to check my models for a particular variation or previously unnoticed variation. The thread about variations was no diferent. Andrea Gurdon, a knowledgeable collector, (but no Sande Schneider) weighed in on a question about Breyer's Quarter Horse Gelding.
Here's what she said:
The "Supermuscled" Quarter Horse was really early - my Buckskin with eyewhites is one. This is the best photo I came come up with in a pinch:
The barrel is where the bulk of the changes can be most clearly seen. Here's the SR Matte Bay:
Aside from the muscles being toned down, almost all the muscle definition on his barrel is removed and he got a tummy tuck! The muscle striations on the opposite side of his neck are also buffed away.
There is a third variation of this mold that's in between the two. I don't have all three in front of me right now to point them out, point by point though.
I have examined my five QH geldings, and I am pretty certain that my early bay one is a "supermuscled" piece.
