Congrats on picking up this excellent looking helmet for $325! What a great find in a local "junk" shop, as this piece is far from being "junk". It's in great shape!
I can see a little better the unit marking inside the helmet in one of your photos. Can you confirm that it reads: "F.A.R. 17"? If I'm seeing things correct from your photo, that would mean Field Artillery Regiment 17, which was a Prussian Artillery Regiment. The helmet would have used an artillery ball top instead of the spike.
The M15 removable spike is the shape and type used on the Herman Weissenburger & Company Model 1916 "Jaeger zu Pferde" lobster tail helmets. The shape of this spike is very distinctive in both the height and style as being used on that particular maker's Jaeger zu Pferde helmets , and normally not seen being used on the leather body helmets such as this one exhibits.
Good luck finding yourself an original German trench mace. A real one will set you back $600 to $700 or even more. Sounds like you've caught the "pickelhaube virus" of which there is no known cure!
Again, congratulations on this great find!
P.S. I'll attach a photo of a Herm. Weissenburger & Cie. Jaeger zu Pferde helmet I bought last April. You'll notice the tall, distinctive shape of the spike that is normally found on this maker of Jaeger zu Pferde helmets.
Again, great 'haube Todd! You can be justifiably proud of this one, incorrect spike or not.
Thanks everyone, cheers.