From what I have seen over the years most of the Imperial German steel helmets that have been at gun shows have had missing liners ( that's New Zealand shows pre internet days!). It was not uncommon to see a $40 shell at every show, the camo's were never as prolific and I had only seen a few before the internet opened up the accessibility for collecting.
I have one more battle damaged camo that I hope to get later this year when it is sold, I missed that particular helmet 30 years ago when it was sold for $35 (school kid then with no money back then, now just a big kid with no money). It has nice paint, no liner and I have a suspicion that it belongs with the damaged bayonet I have just posted. "when" I buy the helmet (being optimistic) I will be talking with the guy that sold these items back in the 80's and see what he remembers about them as they are "local" items from my perspective. I will certainly post it here if and when I manage to secure it.
Maybe the damaged helmets liners were broken out when hit or "contaminated" and therefore removed?
Andy