Comparing: S-51 vs. SU-14-2 vs. 212A

Developed by the Grabin Central Artillery Design Bureau in the fall of 1943. The S-51 passed trials successfully in the spring of 1944, but never entered mass production.

A "Special Purpose Heavy Triplex" self-propelled gun developed from 1932 through 1937, with two prototypes modernized in 1940. It never entered mass production.

Technical requirements for the 212A self-propelled gun were developed in August 1940. The Special Design Bureau No. 2 of the Leningrad Kirov Plant started development based on the KV-220. Blueprints for the vehicle were ready by February 24, 1941, but a prototype was never manufactured. By August of 1941, development was passed on to the UHMP (Ural Heavy Machinery Plant), but a prototype was never built.