The description of the guitar- which I do remember hearing called Cello guitars in the early sixties- sounds typical of German built archtops.
Hofner is the best known,but Hopf, Hoyer and Hagstrom (not actually German and what was the "H" thing about?) all made them.
there are some useful links to European guitars and a lot of pictures for comparison here:-
Hofner Hounds Website
Cheers
Dave