In addition to the small locomotives of power class I, a more powerful variant was also produced. The definition of power class II provided for an engine output of between 50 and 150 hp. A total of 65 prototypes were made by a large number of manufacturers before the final, standardized design for the series was determined in 1932. Although these looked very similar on the outside, there were different drive concepts.
Most of the locomotives drew their power from a diesel engine, but several also had the benzene or Otto engine that was common in railcars and small locomotives at the time. Either a hydraulic transmission, a mechanical manual transmission or, in some cases, an electrical power transmission served to transmit the power. Individual pieces were built with steam engines or as electric storage locomotives. The designation of the locomotives consisted of a K for “Kleinlokomotive” (small locomotive), an ö or b for diesel (oil) or benzene engine and f, e or no additional letter for hydraulic, electrical or mechanical power transmission. The steam locomotive ran as Kd and the storage locomotives as Ka or Ks. Finally, Roman II followed for the power class. The Köf II was selected for series production, i.e. the variant of the diesel locomotive with hydraulic transmission.
As with the Köf I (which was actually only introduced later), great importance was attached to simplicity and a compact design. Initially, a braking system based on pedal force was used because the loads being pulled were small. The doors were also initially open, which also had the advantage of quick entry and exit when shunting. The low body made it possible to load the slow vehicles onto freight wagons and move them to another location without exceeding the regular loading gauge.
These locomotives were used for a very long time on both sides of the Iron Curtain. The Bundesbahn even built more than 700 new Köf II with some improvements. The main changes were engines with 128 hp, air brakes and a closed driver's cab. The existing pieces were gradually rebuilt until 1974 so that they largely corresponded to the new builds. The last of the Bundesbahn locomotives, later designated as the class 323, were retired by DB AG in 1999.
In the GDR, only a few individual pieces were made as replicas, but LKM Babelsberg used the basic design as the basis for the N3 and N4 models with only 60 or 90 hp. Later, also based on the original model, the V 10B, V 15, V 22 and V 23 were created, each with an output of between 100 and 220 hp corresponding to the designation. Most of the pre-war locomotives were given a mechanical gearbox and from 1970 they were classified as class 100. More than 300 of these were included in the renumbering plan of the combined DB AG, but in contrast to the Bundesbahn machines, they were classified as class 310.