By early 1943, a decision was made to install a 128 mm gun on either a Panther or Tiger I chassis as a heavy assault gun. The Panther chassis was considered unsuitable after a wooden mockup of the design was constructed. On 20 October 1943, another wooden mockup was constructed on a Tiger II chassis, and presented to Hitler in East Prussia. Two prototypes were produced: One was a version fitted with the eight-roadwheel Porsche suspension system (Serial Number 305001) and another version was equipped with the Henschel nine-overlapping roadwheel suspension system (Serial Number 305002), as used on the main-production Tiger IIs constructed by Henschel. They were completed in February 1944. It was originally designated as "Jagdpanzer VI" but was later renamed as the "Jagdtiger" and received the Sd.Kfz. 186 designation as its inventory ordnance number.