This self-propelled gun was one of the most interesting Swiss-made armored vehicles, despite the fact that it was never accepted in service. It was not totally original per se - it was more like an assembly of existing solutions invented by other parties and it was by no means bad, the program was cancelled for economic reasons, not design ones.
The requirements for the NK2 were laid down in March 1943 with the real design work starting on 28.1.1944 when the SPG parameters were finalized as such:
- 75mm gun or 105mm howitzer
- maximum depression: -14 degrees
- maximum elevation: +26 degrees for the gun or +38 degrees for the howitzer
- telescopic and periscope sights available
In the end, the NK2 ("close combat gun") project took a while to develop, as many as 4 variants of the vehicle were considered. In January of 1946, a single prototype was made - the only one of the four that would be actually built. It weighed 24 tons and was armed with a 75mm L/49 gun. Its frontal armor was 70mm thick and its maximum speed was 50 km/h. The vehicle had a frontal transmission that resembled the American design actually, but was of the Wilson type (clearly influenced by the Czechoslovak-made Panzerwagen 39). The hull was in turn heavily influenced by the French (partially cast, partially bolted with curves). The crew consisted of five men - commander, loader, driver and two gunners, a legacy of the main weapon being originally an AA gun. The vehicle was propelled by a 12-cylinder Saurer 16 liter CV1DL engine, producing 300 horsepower. The suspension was a mix of Czech (drive sprocket, support rollers), American (roadwheels) and German (Panzer IV-style idler) influence.
Even though the self-propelled gun concept was becoming somewhat obsolete, the vehicle turned out to be quite good, especially considering the fact that Switzerland was not exactly experienced in tank design at that point. The vehicle was assembled and tested in Thun, where it is currently located as well. Unfortunately, after two years, the project was cancelled for economic reasons. The Czechoslovaks offered Switzerland the 15-ton G-13 tank destroyer, which was already mass-produced. The NK2 mantlet by the way comes from a G-13 as well.
Despite not being mass-produced, the NK2 actually turned out to be fine. Despite some similiarities to the G-13, it was completely originally developed.