No, this isn't fiction! The real machine is featured in our Spotlight GVT-04 and is an incredible piece of scratch building.
In 1975/76, five Gefechtsfeldversuchträger (GVT, battlefield test-beds) were designed and built for the testing of the mobility and the basic concept of a twin-gunned machine. Two full-size VT twin-gun prototypes had alreay been built by MaK in 1974/75, largely based on redundant MBT-70 chassis. The GVTs were much smaller than VT1-1 and VT1-2. GVT 01-05 were only fitted with dummy guns and laser fire simulators. This concept was a potential replacement for Leopard 1, and was developed in parallel with Leopard 2. The GVTs used Leopard 1 running gear, but don't have much else in common as you can see in the model.