...Hmm my Russians not so good, now I have seen photos of this gun being used in the battle of Berlin, so WW2 I would buy it, and I suspect everyone who has purchased WW2 Germans and Russians would too.

The same chassis was used for three different barrels of different calibers, the 203mm being the most common. Post-WWII Soviet Army used a wheeled version. So plenty of options or conversions.

Mike Bunkermeister Creek
Bunker Talk Blog