Very Nice.
The enrolled GdC and GKR M15 helmets were indeed made of copper-plated steel (copper-gold plated).
Here we have a model with an ‘Officer’ finish, but with a crest eagle, for a private soldier.
Cockades for ‘Portepee’, like a Rittermeister.
Conclusion:
Fancy’ helmet M15, for a senior non-commissioned officer known as a “Portepee”.
NB Almost all GdC or GKR M15 helmets in copper-plated steel have lost their gilding over time.