PzKpfw III
Daimler-Benz, Krupp, MAN, and Rheinmetall all produced prototypes. Testing of these took place in 1936 and 1937, leading to the Daimler-Benz design being chosen for production. The first model of the Panzer III, the "Ausführung A." (Ausf. A), came off the assembly line in May 1937; ten, two of which were unarmed, were produced in that year. Mass production of the Ausf. F version began in 1939. Between 1937 and 1940, attempts were made to standardize parts between Krupp's Panzer IV and Daimler-Benz's Panzer III.