In October 1938, Krupp-Grusonwerk began production of the Panzer IV Ausf. D (series 4/BW and 5/BW), producing 229 tanks by October 1940, while the remaining chassis were used for bridgelayers, Dicker Max self-propelled guns and Karl ammunition transporters. The Ausf. D modification received a 30 mm thick broken frontal plate (similar to the A version), a new Kugelblende 30 ball machine gun mount, an improved driver's view with a K.F.F.2 periscope and modified engine compartment ventilation. Important updates affected the chassis, where five balancer travel stops appeared on board, and the turret, which received an external gun armor mask 35 mm thick and modified viewing devices with 90 mm armor-piercing glass. The tank's combat weight increased to 20,000 kg, and the ammunition for the MG 34 machine guns was increased to 3,150 rounds.
