Germany - Imperial
Imperial German “Pickelhaube” M15
This is a 1915 Prussian helmet with field-gray metal fittings. The spike can twisted off and removed, which made it easier to fit the canvas field cover. Also, since artillery units had round balls on the top instead of infantry spikes, it was easy and inexpensive to swap things around as need be. This was particularly practical later in the war when steel helmets were issued to the men in the trenches, who, when leaving the front, swapped their M16 steel helmets with the pickelhaube worn by the replacements sent up from the rear. Found this one at Aladdin’s Lamp Antiques in Highland Park, Illinois back in 1970.

Close-up of the universal fitting for either an infantry spike or an artillery ball.