All of the three that I've seen were housed in grey metal, and of fairly good size, like a file cabinet. I don't know that I've ever seen a schematic or a owner's manual, not even sure that Gunderson ever wrote anything like that. As you mentioned, they are very rare, and only a very small number were ever produced. Still, the things are worth their weight in gold to a serious reloader. The closest thing to them that's ever been produced is probably the Prometheus, which is likewise very limited in production, and very pricey indeed.
Let me drop a line to Mid and see if he has any pictures or knows of a schematic on these. Drop me a PM and I'll see what I can dig up for you.