General Information: The Model 1931 was the helmet worn by Norwegian troops at the time of the Nazi invasion. It was initially manufactured in Sweden, but later was produced in Norway by the Raufoss A.F. company. The M31 closely resembles the Swedish M26 except that it has a small crest on the top of the helmet. There was a version of this helmet that had an oval badge with the Norwegian lion embossed on the front. During the Nazi occupation period many M31s were reissued to the Nasjonal Samling Politi, the Quisling collaborationist police. These helmets had transfer decals on both sides for the NS Politi.
Displayed Example: This helmet appears to be unaltered from its Second World War state. When I bought the helmet, it had a handkerchief tucked into one side of the liner. By all appearances this is a period feature. Why was this done? My thought is that the original owner was using the handkerchief to protect himself from the elements, either wind or sun or both. It is an interesting feature that speaks to some long-ago small episode during a tragic time.
Collector Notes: The Norwegian army in the Second World War was not large. Therefore, there were not a great number of helmets produced for its use. Many of the M31s were reissued to the Quisling police and my personal observation is that these reissued helmets seem to be more common than the original, unaltered ones used at the time of the German invasion.
* Citation sought
 Marzetti. 2003. pp267