Here's a Supreme Audolyzer model 562 that I just obtained from a lady that is getting rid of her husband's old radio stuff. This version is in a wooden case; but, the back is missing. Did these have a metal or wood back? I'm going back over there soon and I hope I find the back somewhere.

Steven Johnson is pretty much the expert on these beasts I think.

http://www.stevenjohnson.com/supreme/index.html

He's a regular over on ARF, along with some other experts on old test equipment.

http://antiqueradios.com/forums/

John