Hi Jerry!
Great to have you around!

It seems that both derr reitmeister and greatwar's helmets have an extra on the helmet on where the spike base is attached.
I can only think of Ken's more plausible answer. He said that the owner was probably a Fanhrich (officer candidate). A fanhrich was enttled to wear/use SOME of an officer charateristic, well, I dont have a GdC myself, so this opinion is based on assumption and reference alone, I could be wrong.
In Stubbs book, page 140 & 141, there is a Fanrich GdC, it has the step visor just like officer's, the parade eagle is also wearing a gilded crown just like officer's, BUT the spike base is oval/football shaped, which is EM's style, officer's used a clove leaf/cruciform like spike base.
Perhaps the owner entered the service as a Fahrich and was later promoted to Oberleutenant, so Ken said, and why bought 2 expensive identical helmet, just drilled more holes to accomodate the clove leaf spike base, the oval's former holes will be covered by the clove leaf anyway.
But i cant think of any answer for Dean's 1867 GdC, perhaps it was true as well, it has been in service since at least 1867-1889, when the EM kurassier's front visor was changed from step visor like officer's to a rounded one. Perhaps again, the wearer was involved in wars, field duties and one way or another, the spike was detached/torn and, well, field repair depot didnt always have exact spare, hence the extra holes.
We need more pics for the Greatwar.com GdC helmet. I am curious whether the rear raised ridge reinforcement is present.
Pls check out Tony's great referance abt Kurassier's helmet, infact he own 2 of them, a 1862 and 1889 EM kurassier
http://www.kaisersbunker.com/pt/metalhelme.htmNotice also the different spike base on both helmets, clove leaf for officer's and oval for EM.
But if I had the money, I will go for greatwar's, its an older 1867 GdC!
Hope this helps,
Mush