This is a real prototype.........
"In September of 1939, German High Command ordered Krupp to design a heavy panzerjager armed with 105 or 128mm gun that would be able to destroy enemy tanks and heavily fortified positions (such as pillboxes). In early/mid 1941, Krupp-Gruson produced two prototypes of such a vehicle and on March 31st of 1941, first was presented to Adolf Hitler. The Fuhrer ordered further development of heavy panzerjagers armed with either 105mm or 128mm guns. He also ordered that the production of Selbstfahrlafette 10.5cm must start in the Spring of 1942, but it was later on cancelled in favour of other vehicles.
Selbstfahrlafette 10.5cm was armed with Krupp's 105mm K 18 L/52 gun with limited traverse of 8 degrees (left and right) and based on modified Panzer IV Ausf A's chassis. The gun itself was developed by Krupp and Rheinmetall from 105mm sK 18 L/52 heavy field gun and was mounted with a muzzle break. The gun was capable of penetrating 111mm of 30 degrees sloped armor plate at 2000 meters. It was mounted in lightly armored (armor protection ranged from 10mm to 50mm), open at rear superstructure and for local defense machine gun (7.92mm MG34) was carried inside as well. Vehicle was powered by Maybach HL 120 TRM engine with total power of 300 horsepower (same as Panzer IV) allowing it to travel at the speed of 40km/h.
Originally, two prototypes were assigned to Panzerjager Abteilung 521 in preparations for upcoming attack on Gibraltar. At the beginning of Operation Barbarossa, both were assigned to 3rd Panzer Division and were troop tested. One of them was lost when its ammunition exploded (it was then captured the Soviets) and the second one was brought back to the factory in October of 1941. Both prototypes proved to be very effective against Soviet KV-I, KV-II and T-34 tanks. Serial production did not take place, while even limited numbers would prove to be very useful to the front line troops faced with superior Soviet armor in 1941/42."
