Imperial German M16 combat helmet or 'stahlhelm'

An Imperial German M16 combat helmet manufactured by J. & H. Kerkmann, Ahlen/Westfalen, stamped 'K64' near one chinstrap bale, with full leather liner with three two-finger pads and chinstrap, very faintly inscribed to the interior with a name and possible unit

Notes: J&H. Kerkmann only manufactured helmets in this size. Their output of approximately 125,000 helmets represented around 1.7% of the total produced during WW1.