Wikipedia
The Schlörwagen (nicknamed "Egg" or "Pillbug") was a prototype aerodynamic rear-engine passenger vehicle developed by Karl Schlör (1911–1997) and presented to the public in 1939.
Schlör, an engineer for Krauss Maffei of Munich, proposed an ultra-low drag coefficient body as early as 1936. Under Schlör's supervision at the AVA (an Aerodynamic testing institute in Göttingen) a model was built. Subsequent wind tunnel tests yielded a drag coefficient of only 0.113, incredible then and still extremely impressive today. For a functioning model, a Mercedes-Benz 170H chassis, one of their few rear-engine designs, was used. The aluminum body was built by the Ludewig Brothers of Essen. Subsequent tests of the motorized model showed a slightly higher but still impressive drag coefficient of 0.186. A year later it was unveiled to the public at the 1939 Berlin Auto Show. The project was shelved with the onset of World War II and mass production was never realized. The model was later taken to Russia and fitted with an external propeller engine. The whereabouts of the sole functioning model remain unknown.