I just got my paws on an out-of-print copy of "Roller Coasters, Flumes and Flying Saucers - The Story of Ed Morgan and Karl Bacon Ride Inventors of the Modern Amusement Parks". There is some interesting info in it about the cast aluminum horses and the carousels they were on.
First off, Morgan and Bacon (aka Arrow Development Co) were the first to create an all-steel carousel. It was a little one, the 20' diameter type with small horses and it was one that I rode as a kid. It was up in Alum Rock Park in San Jose CA.
The horses were all made of cast aluminum, except for during the Korean War and for a short time in the early 1950's they made the horses from magnesium. But they didn't hold up well and would tend to crack when they cooled.
One of the partners commented that these early metal carousels were designed to be portable, because they were often purchased for traveling carnivals and would only be in place for three days or so before being dismantled and transported. He said that from a design standpoint they were fabulous, because they would break down and go together quickly and easily. But that from an asthetic standpoint, he was not proud of how the carousels looked. But I have to say we kids loved 'em anyway! (and still do!)
Here'a a couple of photos from the book, the first showing the "plug and mold" for my model of horse:
The second showing one of the carousels which looks just like the one my horse came from at Happy Hollow. Same basic design but the photo is clearer than the one posted above from the 60's. Looks like the horses with their heads raised like mine are on either the center or interior row. The horses with the heads tucked are all on the outside row.