In 1925, the Deutsche Reichsbahn initially bought a few experimental small locomotives. These locomotives had internal combustion engines, which were later to replace steam traction. After the tests had been positive, the Reichsbahn classified further procurement into two performance groups starting in 1931:
– Power group I: Locomotives up to 39 hp and max. 30 km/h speed. They were intended for switching operations in small stations under simple conditions
– Power group II: Locomotives from 40 – 150 hp. They were intended to enable trained personnel to carry out shunting tasks in one-man operation
The letter K was introduced to identify the locomotives, followed by an index for the type of engine used: b (benzene) for gasoline engines and ö (oil) for diesel engines. For locomotives with a liquid gearbox, the letter “f” was added. On the German Federal Railways they were known as class 311 or 321-324 from 1968 and on the German Reichsbahn as class 100 in 1970.

The Kö 3504 was a plant locomotive that entered service at Chemische Werke Albert in the mid-1950s and was given the number 35-04 there after the company was taken over by Hoechst AG. In 1983, the locomotive was taken out of service and donated to the vehicle collection of our museum.