Hello,
congratulations for this beautiful sharing. I like it.
Simply, a small remark (constructive to correct):
The helmet "Eigentum", does not conform because it shows two inconsistent elements:
---If it is a helmet of an Einjährig Freiwilliger, it must have troop cockades, and no tip base stars. It has the correct "troop" Guard star.
---If it is an officer's helmet, it must have officer's cockades, tip base stars as here, and the enameled Guard star, of the officers.
Only one plausible explanation for your helmet, it could be the helmet of a "0ffizierstellvertreter", i.e. a "Compagnie-Feldwebel" promoted to 0fficer, at the front, as a provisional of war. (Second lieutenant, not graduated from the officer school).
A peacetime Fähnrich would have no base stars, officer's cockades, and an enameled Guard star.
The second photo shows a Guard officer's helmet, with the tip attachment stars and the enameled Guard officer's good star.