Design No:- Object 704. Built:- 1945 at the Chelyabinsk Kirovsk Plant. Main armament:- 152mm gun-howitzer, model ML-20SM. The standard ISU-152 replaced the SU-152 and used the same 152mm gun-howizter, but mounted on an IS-2 Heavy Tank chassis. ‘Object 704’ was a prototype developed using elements of the IS-2 and IS-3, and although being the best protected of all Soviet self-propelled guns during WW2 it was complicated for the crew to operate and did not go into production. This remaining prorotype is on display in what is best known as Hall1 of the Kubinka Tank Museum, although its official title is now Pavilion 1 in Area 2 of the Park Patriot museum. Kubinka, Moscow Oblast, Russia.