I saw one close up many years ago. The owner was a collector. The version I saw was basically leather, and my (imperfect) memory leads me to think it dated from WW1.
The spike was removable merely by pulling on it firmly. The bottom of the spike (the bit which would ordinarily be concealed had it not been yanked from said helmet) had a surface that was basically flat and round, but with a texture that had been clearly scored in the manufacturing process to roughen it.
The owner told me the idea was that a soldier would pull the spike out and use the roughened surface as a striking mechanism to ignite the pretty primitive hand-grenades then in use.
No idea if it is true. Could be a retrofitted explanation, but it seemed plausible, given what I could see of the spike and the surface.
Of course, the mere fact that the spike was made useful at some point (heh) in its history does not mean that that was the original purpose for which it was put there.
Military headgear has traditionally been designed to make the soldier look taller and more impressive. Stories of its battlefield utility have generally been made up afterwards.
Trivia:
From about 1900 to 1917, the U.S. Army dress uniform included a helmet. It was not for battle, but only for parades. It had a detachable crest. Infantry wore a spike, making it look a lot like a pickelhaube. Cavalry wore a plume, making it look a lot like the “Prince Albert” helmet worn today by the mounted guards at Buckingham Palace.
One you realize that most early-WWI helmets had something up there, crest, ridge, feathers, flat-topped spike thing, ball, etc, then you’ll see that spike was just another decoration.
Here’s a book review from Amazon, talking about US helmets, just pre-WWI
"The plumed and spiked dress helmets worn by the U.S. Army between 1872 and 1904 have become exceptionally rare today. But these helmets have intrigued collectors and military historians since their use was discontinued shortly after the turn of the 20th Century. They were the most colorful helmets ever worn by the American Army and they are more reminiscent of Europe than North America. Following the defeat of France during the Franco- Prussian War, the German army was seen as the most powerful in the world. Their tactics, arms and uniforms was emulated and the United States was no exception.
Beginning in 1872, the plumed shako was replaced by a tall, bell shaped helmet with a deep lobster-back tail and short brim. Mounted soldiers and officers wore cords and flowing plumes in the colors of their branch of service yellow for cavalry, scarlet for artillery, black or orange for signal corps foot soldiers and lower ranking officers wore spikes. Some regiments allowed the use of unadorned white helmets during the summer and tan helmets were worn by enlisted men for fatigue duties.
Because these felt helmets were quite delicate, their survival rate is not high. Over the years, numerous reproductions have been offered to collectors, reenactors and even to military units wearing past uniforms for ceremonial occasions. Many of the reproduction metal parts were struck from original dies and are quite difficult to tell from the originals, as are many of the felt helmets produced in the 1950s and '60s.
Mark Kasal and Don Moore have studied and collected the original Model 1872 and 1881 helmets for years. They used their expertise and collections, as well as those supplied by authorities in the field and museums to explain the history of the development and use of these helmets. They have also described on a part-by-part basis, each component of the helmet and described the differences between original and reproduction parts. "
The germans were still wearing odder headgear at the start of WWI wiki"The Imperial German field grey of 1910 retained a number of traditional features such as spiked helmets, shakos, busbies and coloured piping from the older uniforms.
I am sure this was mentioned in the older thread, but…
The original purpose of the spike on the helmet was to deflect a sword blow away from the head. The helmets of the time were just leather and would not stand a chance against a sword.
Of course then it became decorative, with artillerymen having cannon balls on theirs, the Kaiser had a chicken on his and so on. You know how it happens, peer group pressure.