Otherwise known as the KPz 70, the MBT-70 was one of those attempts at making a standardized MBT for NATO's members (or, at the very least, standardized between the US and West Germany), only for it to fall apart on account of developmental contention and conflict of interests between the involved parties. Disagreement over things like the gun and engine were frequent, and just in general the US and Germany seemed to struggle immensely when it came to cooperation throughout the program. Unsurprisingly, all of this, combined with the rising costs for development of the tank and Germany starting to get cold feet on the project entirely, led to the inevitable downfall of the MBT-70 program. In the aftermath of its failure, the US and West Germany went their separate ways, developing their own tanks. Germany would begin to develop the Leopard 2 MBT on their own, while the US would continue to work on the MBT-70 (now dubbed XM-803) for a short while, before finally cancelling the whole project and instead redirected funding and technology to the M1 Abrams.

This specific version is one of the earlier Pilot models, featuring a noticeably squatter hull (or maybe the fort has it set like that to show off the adjustable suspension, since there's another MBT-70 model that's present in the collection). Not sure if the gun on this model is different from the other one, though it could just be a perspective problem with the camera. Very modern-looking for the time it was developed.

I almost made the mistake of saying that the German versions of this tank carried more conventional 120mm guns, but upon doing some more reading, this is not the case; while there was some talk about doing something like that, it only really got as far as a wooden mockup, and the 120mm was in fact part of a completely different tank project called the Keiler. Additionally, the Leopard 2's development was derived from this project and not from the MBT-70. (And right as I add that, I'll probably find out I've been bamboozled. Oh well, I'll edit this out if that's the case.)