🇺🇸 The American 'M1 TTB':

Built in the 1980's the M1 Tank Test Bed was an attempt to increase the protection of the crew without adding tons of additional weight. In this approach they moved the crew into the modified hull and used an unmanned turret.

The main weapon is an autoloaded 120mm M256 smoothbore gun.
The TTB was powered by a 1500hp Avco Lycoming AGT-1500 turbine engine and had a top speed of 70km/h.

@WheelsOfDefenseGlobal