This is a large turretless tank destroyer based on the excellent chassis of the MBT Mark II. Although the concept is obsolete, the design bureau still decided to make one. In the big armoured superstructure is housed a gun similar to that on the MBT M2, just that it fires hypervelocity shells.
Great TD! Man I'm going to have make one now, to keep up with you ;). The overall shape brings to mind the Jagdpanther, but with your own style and of course your own chassis design. Let me guess, next up is a SPG varient?