Willy Krenkel's Eigenbau which looks distinctly Cooper inspired. It may have had a Norton engine. Willy competed in the East German championship from 1956 through to its final year in 1959.
He achieved a number of good results including second at Bautzen in June '57 and fourth at Bernau in May '59.
Some results for Willi and his eigenbau:
If you have any more information or pictures, please let us know.