General Information: I have a wonderful reference book that tells us everything there is to know about the Polish wz.31. Unfortunately, it is in Polish and I do not know what is says. I have to rely, therefore, on the scant resources available to me at the moment. Based on my personal observation, most of the wartime wz.31 helmets seem to have been made from 1936 to 1939. They were generally finished with an anti-reflective olive brown paint although smooth paint was also used in the pre-war period, but to a much lesser extent. The anti-reflective effect was achieved by mixing bits of cork in the paint. This is referred to as “salamander” paint finish, or sometimes “salamandra” which is the genus name of several species of salamander native to Poland. The unusual chinstraps were unique to Polish helmets. The wz.31s are marked on their interiors in black ink with the name of the factory, either “Ludwików” or “Silesia.” Below that is a lot number followed by a two-digit number representing the year of manufacture. The Poles manufactured approximately 300,000 of these helmets for use by their armed forces prior to the start of the Second World War. Production ceased in 1939 after the partition of the country by Germany and the Soviet Union. Production resumed in the post-war period with a version of the helmet referred to as the wz.31/50. The wz.31s were also exported to Persia, Albania, and Republican Spain.
Displayed Example: I purchased this helmet from eBay several years ago. It was one of the helmets manufactured by the Ludwików company. It is stamped “36” for the year of manufacture: 1936. It is complete but for two missing pillows behind the two rear liner pads. The pillows may have been deliberately removed to accommodate the original owners head size. This was a common practice with similarly designed German First World War helmets and was likely done to Polish helmets as well for the same reason.
Collector Notes: The wartime versions of the wz.31 are now very difficult to find and they are fairly expensive. The prices seem to have lurched upwards in the last few years. They used to sell for around $1,000, but two were sold at European auction houses recently for $1,900 + buyer fee, and $2,100. It should be noted, however, that both helmets were in top condition.
The post-war version of the helmet, the wz.31/50 are often doctored to look like wartime versions of the helmet. This usually involves repainting the smooth painted helmets with something that looks like the cork infused anti-reflective paint used on the older helmets. This is a difficult effect to replicate well and the fakes can often be identified through comparison with originals. The wv.31/50 had extra rivets. Instead of two rivets on the front, the newer helmets had four with two paired one on top of the other. In back instead of two rivets, there are three, all stacked vertically.
 “Mark-ski”. Wz.1931. HelmNet (private forum). Accessed 4/20/22
 Dagnas. 1984.
 Wikipedia. Hełm wz. 31. https://en.wikipedia.org/wiki/He%C5%82m_wz._31#:~:text=31%20(helmet%2C%201931%20pattern),stages%20of%20World%20War%20II.