A German M18 helmet. A so-called RZM version designed like a WW1 period time helmet.

This example was originally issued to the Allgemeine-SS. It was painted black and came with two decals attached by the factory. You can still see them hided by field grey paint.

After some time the black helmet was overpainted with fieldgrey color to wear with the SS-VT. It received another set of decals which are still around 85-90%. So this helmet shows four decals attached in total.

This special helmet was published in "German World War II Helmets & Headgear" byJan Meland and Gisle Jontvedt on page 44 and 45. Please see last pictures. 

The liner is still flexible. M16 style of leather belt inside. One loose part of a rivet. 
Size 56

Chins strap: soft. Unarked. 
Markings: No markings to the shell visible. There might be some to the inside reverse but scratches hide it. Hard to make out. 

Named to the liner.