As Wikipedia says, Fuldamobil is the name of a series of small cars produced by Elektromaschinenbau Fulda GmbH of Fulda, Germany, and Nordwestdeutscher Fahrzeugbau (NWF) of Wilhelmshaven between 1950 and 1969. So now we know the big picture.
Although Fuldamobil was German, it seems that this car in particular was built at the factory in Haelsingburg, Sweden, and is part of the penultimate series of this model. It seems in excellent general condition.
The seller says that the car is driven by a Sachs engine of 198cc but as far as we know the two-stroke engine Fichtel & Sachs was 191cc while the last series (1965-1969) was pushed by a 198cc Heinkel engine; It seems that the car drives well and is at $15,500 here in Little Rock, AR.