John,
The spike screws off in only one piece. I was told, such "Versuchshelme" have been worn by only three "test" units:
- the Lehr Infanterie Bataillon in Berlin, geographic center of the Reich (very special unit that tested all sorts of new equipments, uniforms, weapons, but also fight tactics and strategies)
- the Grenadier Regiment 3 in Königsberg, in the very east region of the Reich
-the KJR145 in Metz (Königs-Infanterie Regiment), in the very west region of the Reich
Here a very rare pict of 17 such helmets, as they were introduced 1906 in the KJR145 with the new Felduniform:
View attachment 18249
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Philippe