This is an extract from the Polish booklet on the wz.31 helmet by Kloskowski and Rolewski (part of the 'Wrzesien 1939' series, Tome 85, 2016).

Its a substantial booklet (60+pp with lots of excellent illustrations) which I intend translating fully eventually (it is Google Translate that has got better, not my Polish!) but this bit is from the end, covering the post-WW2 developments. Once again, thanks to Piotrek for sending me the booklet some years ago.

start quote -

After World War II, the Polish People's Army used many available helmet designs (Polish models 1931, Czech model 1932, Italian M33, English Mklll, American M1, Soviet ssh1939 and 1940 and even German). In 1950, similar to the Soviet ssh.1939, the helmet wz.1950. This solidly made helmet was produced at Kielce Metal Products Factory and Huta Silesia and had the chinstrap and lining copied from an Italian helmet M33, and can be considered a successful construction.
In 1964, a group of designers led by Colonel Eng. Romuald Zimny of the Military Institute of Armament Technology developed detailed technical conditions and methods for acceptance tests of the new helmet design, which was adopted and implemented for production on April 21, 1967.
Its side profile clearly resembles the Polish pre-war helmet of wz.1931. The shell of the helmet is made of 1.4 mm thick special steel, and its weight is about 1.5 kg. It has a peak and a delicate neckline, whose edge is bent outward and softened by grinding. A leather two-part chinstrap (with a buckle with a pin) is riveted to the bell with brackets.

The liner consists of a cut out leather strip attached to a steel rim, fastened with a cross bolted on the top of the helmet. The liner solution was copied this time from the English Mkll helmet.
In 1977 a modification of the liner appeared, designed by Jerzy Okraszewski and Henryk Andryszczuk. This liner consisted of a cap sewn from green synthetic tape and 15 mm wide leather straps tied at the top with a shoelace. It was mounted in the same way as the previous type. It was more comfortable, guaranteed better ventilation, and an additional occipital strap (copied from the American M1 helmet) held the helmet better on the head.
Wz.1967 was produced in Huta Silesia in two sizes of shell and five sizes of liner. They were painted in different colors: green (for land forces and ZOMO - pilot version), gray-blue (for aviation, navy, militia), blue (for UN units) and light-brown (in the export version to the Middle East). On the front of the helmet, they were usually painted with a template or eagles were placed as decals depending on the purpose. It is interesting that in the prototype phase the possibility of using "Salamandra" rough paint and lining according to model 1931 was considered. This practice was abandoned due to anticipated difficulties in renovating helmets in military units.
The wz.1967 was factory-fitted with a masking net equipped with a veil lowered on the face when needed. The color of the mesh was matched to the color of the helmet.
Wz.1967 can be found in the Polish army to this day, and their modernization consists in using a cover in camouflage colors.
Wz. 1967 is the last model of the steel helmet of the Polish army and, judging from developmental tendencies, this title will remain with it forever.
In 1970 a patrol helmet with the shape of a helmet wz.1967 was produced, but made of fiberglass.

In retrospect, it can be assessed that the wz.1931 was the most modern helmet of its time, and its designers deserve the highest respect for courage in implementing modern engineering thought! Design novelties appearing in other helmets of that time were combined for the first time in one model.
The Polish helmet wz.1931 marked a new direction in the development of protective headgear and was ahead of other constructions by 10 to 20 years. Production optimization was used for the first time, deciding on one universal shell size, no more complicated roll-up of the helmet edge (the Germans introduced it only in 1942), the number of surface bends was reduced, weakening ventilation holes were removed, no signs were used, no combs or other unnecessary decorations. The modern, anti-reflective surface of the helmet was the first factory-used in the world (copied by the US Army in 1936 for the M17A1 helmet). The leather chin strap and clasp were thought-out and ergonomic; easy to use even with thick gloves.
The helmet passed the battle exam in 1939, enjoyed great success in partisan units and the Warsaw Uprising. It was also used in the LWP, and in the 1960s became the prototype of the helmet wz.1967, used until today.
The helmet’s final verification after decades belongs to the collectors who call it the affectionate "Salamandra". Among military enthusiasts around the world it is an indicator of important collections, and well-preserved exhibits achieve high prices. It is also a very sought-after collector's item for connoisseurs, because its accurate hallmarking and production stability make it possible to determine the place and date of production, and even the names of military quality controllers who thus made history.

Jacek Kijak „Hełmy Wojska Polskiego 1917-1999", Warszawa 1993
Bashford Dean „Helmets and body armor in modern warfare", New Haven 1920
Paolo Marzetti „Combat helmets of the world", Parma 1996
Zdzisław Żyguski jun., Henryk Wielecki „Polski mundur wojskowy", Kraków 1998
Krzysztof Kłoskowski, Jarosław Rolewski „Hełmy polskie", Poznań 2016
Ludwig Baer „The History of the German Steel Helmet 1916-1945", Kalifornia 1985
strony www - dostęp w dniu 15 marca 2016 roku
Miejskie Centrum Kultury w Czarnkowie
Świadkowie Historii
Z HISTOII SOLCA - Strona Stowarzyszenie Przyjacioł Solca nad Wisłą - pod tym adresem nie znajduje się żaden serwis WWW

end quote

This is interesting because among other details the writers clearly do not see the wz75 as a separate helmet type from the wz67, as has been assumed with the designations wz67 and wz75 as used by many collectors. This could be compared to the issue of the British MkIV and MkV, the latter of which may or may not exist, depending on who you talk to.