Sorry, I am adding to the confusion by using the term "NCO". I should have used the correct German rank of "Unteroffizier" when describing the uniform rank itself.
In my particular grouping, this "Unteroffizier" is wearing the standard issued mannschaften pickelhaube with the standard issued cockade which is correct.
Had he been an Unteroffizier mitt portepee he could have still worn an issue helmet but could have opted for a private purchase helmet where he could have added the officer pattern cockade.
Again, I will direct you to Tony's fantastic table of Pickelhaube Rank:
http://www.kaisersbunker.com/hp/class.htm
John