It could be a funerary helmet 
For funerary helmet see "A Record of European Armour and Arms Through Seven Centuries Volume V". Many funerary helmets have been much more heavily adapted when they were hung over the tombs. This helmet shows the typical damage from extensive oxidation and a repaired hole in the crest which would have secured the funerary spike .It has an interesting  ventail  
Congratulation nice find.
		 
		
		
		
		
		
		
		
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