As a private venture, Thyssen-Henschel built a fourth prototype designated TH 301. Completed in 1978, it added a PERI R12 periscope, originally designed for the Leopard 1A4, for the tank commander. The gunner and loader each received a day periscope as well. To enable the crew to fire effectively at night, a low light level television (LLLTV) camera, which moved in elevation with the main gun, was fitted to the mantlet. Furthermore, the tank received a more powerful engine. The improvement program also made provisions to increase the thickness of the armor for additional protection.