It was a testing vehicle called the ST-T it used the same engine from the type61 as the destined to be engine of the type74 had yet to exist and was used to test the hydro pneumatic suspension. It was later fitted with both a functional turret from early testing trials and just the gun in a case mate kind of form to test recoil asorbsion. I feel it would be a great one off goofy vehicle, due to its lackluster armor and poor engine performance i feel like this would be great 7.7-8.3 material, more importantly i would like to see the casemate type be implemented similar to that of the strv103s to spread that style of game play (more hull aim vehicles).
If anyone has any more information about these prototypes please share as i would like to see these two vehicles added.