Instead of the T-54M (Obiekt 140), the T-55(Obiekt 155) was manufactured. The T-55, although closely resembling the T-54, was in fact a substantially redesigned tank with many internal and external differences. Externally, the T-55 used a new turret, similar in shape to the T-54A turret, but without the prominent roof-top ”mushroom” ventilator dome, and as a result, two enlarged ’D’ roof panels. Internal improvements include the new V-55 engine, increase of ammunition to 43 rounds, and other features. Unlike the T-54B, the T-55 dropped the loader’s 12.7mm DShK anti-aircraft machine gun. This version had the initial stages of the PAZ chemical/radiation protective system. The T-55 was accepted for service in the summer of 1957 and entered production in the USSR on 1 January 1958.