On September 9, 1938, following initial testing of the D.W. chassis, In 6 authorized the Heeres Waffenamt to continue with the development of a Panzer in the 30 ton class. With a 30 metric ton weight restriction, a Panzer armed with a 7.5 cm Kw.K L/24 could be designed with armor protection of 50 mm on both the front and sides. Armor plate 50 mm thick was the established standard for effective protection against uncapped armor-piercing shells fired by the German 3.7 cm Pak L/45 anti-tank gun. Officially named the Panzerkampfwagen IV(7.5 cm)by October 31, 1940, it retained the design code name of D.W. along with the new code designation VK 30.01.