A tank destroyer utilizing the 15.2cm M64 gun (an improvement in every way from the ISU-152's ML-20S), the Obj. 268 was the result of a soviet design for a 50-ton TD based upon the IS-8 (shortly thereafter the T-10)'s hull. Only one prototype was produced, now displayed at the Kubinka tank museum.
Couldn't get all of the geometry right, but I think I did a pretty good job. Mounted on the T-10-chassis. Funny thing is, this was actually the first-completed of all of the three new tank models I've posted.