This should be an easy one for the experts to solve quickly for a point
Mada Libelle 250 1947-1949 Germany
German yes but not the car you mention.
Later than the 1940s.
Kroboth-Allwetterroller
Thought a Kroboth too but didn't it come from Czechoslovakia about 1954 rather than Germany?
It is indeed a Kroboth Allwetterroller of 1954.
Manufacturer was Fahrzeug-und Maschinenbau Gustav Kroboth, of Seestall uber Landsberg, Germany who built around 55 cars from his little factory between 1954-1955. A four-wheeler with a Sachs 174cc was also built.
Well done Studhamsmudger - another point for you.
Carnut - Gustav Kroboth, stavba motoru a vozidel 'Favorit' of Sternbek, Czechoslvakia (the same man) also built simple two-seaters in that country between 1931-1932. Around 150 cars were built.
After 1945 he moved to Bavaria where he produced the subject of this puzzle - the "all-weather runabout".
Better luck next time Carnut.
A brochure:
A nice 1954 magazine clipping: