Both the modifications of the chassis - armor thickening to 50mm by riveting 20mm extra armor plates on the frontal armor and lower glacis, changing the driver's hatch from a single door which opened to the right to a two-piece folding door which opened to the front - and the prototype of the new gun and turret were finished in January 1942, the new turret was finished in February 1942. The new 75mm gun was the first Hungarian tank gun which received a horizontal semi-automatic sliding block.