Froggy55:
The design of all these German cabs is very similar, and certainly offered an appreciable space compared to ost standard cabs of the 1950s and 60s.
I would agree with that- the Relaxe cab came out in 1959, but those German cabs were available some five years before. Even the Dutch, with their vast battalions of coachbuilders, were a year or two behind the German metal-bashers (tin hat on) 
.