That is one hard nut to crack. It isn't in any GDR truck/car/tractor book I've looked through. The only similar vehicle I found was the so called "Bornimog", the RTA 0511/60 made by the Institut für Landtechnik, Abt. Schleppertechnik in Potsdam-Bornim. It was further on developed to become the RTA 511, built at first in Traktorenwerk Schönebeck, and later on in the Brandenburger Traktorenwerk. Anything to do with this?