The helmet appears to be an enlisted man's private purchase. The spike looks a little different and seems to have been off the helmet at some point, as I don't see the washers under the nuts. The state cockade is Prussian. Things to look for dealing with the plate; How is it attached? Are there extra holes? Are there marks in the leather that match up (or don't) to the plate's out line. The one thing that does bother me about the plate, is that it comes down over the front visor. The Bayern plates I'm that I have seen come down to just above the visor.
The other helmet posted looks to be an issued type. Not sure about it being an NCO's.