In 1934 a new liner system for German helmets was adopted, namely the model 1931 liner. The new liner took into account the size of a soldier’s head rather than only the helmet shell size. The M31 liner consists of two interlocking metal bands which are connected to each other with 5 steel leaf springs. The leather liner was attached to the inner metal band by small rivets made of aluminum and subsequently zinc-coated steel. The band is stamped with the liner head size and appropriate shell size. The leather part consists of 8 separate «tongues» which are perforated with 5 stamped holes to allow for ventilation. The liners for larger helmets (size 68-70) have 9 leather tongues.
For precise adjustment for a soldier’s head size, a woven drawstring is inserted through a 6th hole on the tip of each tongue. Between the leather and the inner band, a wool strip is attached to improve comfort and to avoid rubbing of the fragile leather against metal. Early liners were made mainly of aluminum parts changing to zinc-coated steel parts in 1940. The M31 liner consists of many parts and the 6 different liner producers that that existed obtained certain components (leather and rivets) from several other manufacturers.
Three M31 liners stacked together. The liner in the middle has an aluminum band while the other two are zinc-coated steel. Note the chinstrap bale (D-ring) on the aluminum example; it is more square shaped than the others which have more rounded corners. Also this aluminum liner is a reinforced type; notice one of the supporting/reinforcing aluminum strips attached to the outer band with 4 small aluminum rivets.
Markings on the inside of the leather. The number 57 indicates the size in cm of the inner metal band and the number 55 is the size for the wearer’s head, which is also is marked with an ink stamp on one of the tongues. The liner has the size of 62 and the size of the outer metal band is measured to be approximately 61 cm. Notice the lacking wool strip which has been cut off and the split aluminum rivets which secure the leather to the metal band.
Markings on an aluminum liner dated 1938. «D.R.P.» means Deutsche Reichs Patent and the manufacturer is Schuberth-Werk K.-G. in Braunschweig. The abbreviation K.G. stands for Kommanditgesellschaft which means Ltd. or Limited. Notice to the left the 2 small aluminum rivets to which the reinforcing plate is attached and to the right the chinstrap bale with square corners.