An early attempt by Daimler-Benz to install a 6-cylinder diesel engine in a Mercedes-Benz Mannheim chassis ultimately failed due to its unacceptable vibration.

1935 saw the successful installation of the smaller OM 138, 2545 cc overhead valve, 4-cylinder engine in a Mercedes-Benz 230 (W21) chassis.

Branded as the 260 D, the car was introduced to the public at the 1936 Berlin Motor Show, although 13 pre-production units were produced the previous year.

[2] 170 pullman-landaulets based on the W21 chassis were built from 1936 to 1937, called the Nullserie and used only as taxis, with a three-speed plus overdrive transmission, without synchromesh on the first gear.

The chassis was based on contemporary Mercedes technology and had transverse leaf spring independent front suspension and swing axles at the rear.