Comparing: Centurion Action X vs. STB-1

The Action X turret was planned to be used for later variants of the Centurion tank. One prototype of the turret was mounted on the chassis of the Centurion Mark 7, and another was used for ballistic trials. The vehicles with the Action X turret never entered mass production or saw service.

In the early 1960s, Mitsubishi started development of a new tank that complied with government requirements for armament and defense. The first two prototypes of the STB-1 were manufactured in September 1969 for trials. In 1970 the prototypes were shown to journalists and participated in a military parade.