Dan, This appears to be a Setra bus. There is a small "SETRA" logo on the small compartment door midway back. They are a German company currently owned by Daimler Benz. Cool old rig.
I don't know what it is but if anyone does it would be Tim Heintz (just google Tim Heintz Designs in FL) or a gal that finds wonderful stuff on Yahoo Groups "Vintage Camper Enthusiasts". Her name is Camilla firstname.lastname@example.org. She is amazing in what she knows or can find out. Good luck...it is an awesome motor home and I would love to find one too!!!