I read a little further now...
Rudolf Stierlen of Rotenburger Metallwerke ordered a four-wheeled car at Wickenbrock in Recklinghausen to improve the not successful concept of the Pinguin. Due to much too high production costs he finally abandoned the whole Pinguin project.
Sectretly Stierlen was about to continue the Pinguin project with another name. But "Hobby" and "Bel Ami" couldn't be trademarked. Motorcycle producer Express was only interested in a four-wheeled car which wasn't finished, yet. Kreidler was interested as well, but the asking price for the whole company was too expensive.