helmet has 6 small rivets. Inside liner is like the metal shells last type : removable plastic circle with leather made of two parts sown onto the plastic. Both leather parts are "loose".

helmet has 3 small rivets. Liner has no plastic at all : the circle is made of cardboard. Liner is made of fine whitish leather (real good quality); one piece leather (not like previous one) like the WWII type but the 8 lugs do NOT have the 5 holes ! None of the parts of he liner can be removed... they are all riveted together to the shell. Between the liner circle and the shell, the are 4 orange "sponge pieces" riveted to the circle (2 in front 2 in back) with 2 rivets probably for confort reasons...This  helmet is a brand new one !!

helmet has 3 BIG rivets...positionned slightly higher than on the other helmets... contrary to the rivets above, those are removable type (just like the Wehrmacht ones). Liner is approximately the same as helmet 2. Has 8 leather lugs but these have the 5 holes. The two ends of leather liner are sown at rear (zigzag stich). In the front, the leather has a nice design made of very small holes (probably for sweat purposes).
The leather is dated 1961 and a second marking 1959. The plastic shell slightly moves up all around the helmet (not straight down like others). To end with, shell is marked 58 (= size or is it production year ?) underneath at rear (it is struck).