Hi Amy,
Thanks for posting this. I'm glad to hear that you are questioning this helmet.
The helmet is a standard Enlisted pattern Kurassier helmet.
And yes, you are correct: the spike is not an enlisted Kurassier spike, but instead it is a standard infantry enlisted spike as of course you realize.
Was the exterior of the helmet chromed, or just highly polished? If the helmet has a brass eagle and a brass spike base as seen in the photos, the metal trim around the edge of the helmet and the domed rivets should all be brass color. Seeing that these parts are shiny white metal leads me to believe the exterior of the helmet was chromed at one point of time.
The chinstrap side post mounts are also the M15 Wartime Kurassier Gray Metal.
Looks like this helmet is an assembly of wartime and pre-war parts, and the exterior of the helmet has been chromed.
Best Wishes,
Alan