According to wikipedia,
Cyclecars were small, generally inexpensive cars manufactured mainly between 1910 and the late 1920s
.
This is from 1949 and is fitted with a much smaller engine tha an average cyclecar of the decades before.
The license plate is a postwar German one, from Lower Saxony (BN = Britsche Zone Niedersachsen).
The manufacturer of this car comes fom Bavaria and its former name is still quite well known.
If I understand my source correctly it wasn´t intended to be a one-off, but possibly was one, though...