I would have to agree that it was likely his Shako, and due to shortages, he was issued what was available. One thing is for sure, if a collector encountered that now, they would deem it to be put-together and "fix" it.
Here is a peculiar one!
The soldier at right was from Mecklenburgisches Jäger-Bataillon Nr.14, but his shako has the distinct front plate of Hannoversches Jäger-Bataillon Nr.10.
Vizefeldwebel Willy Kober, 28 February, 1919 in Reserve Lazarett II, Ziegelhof, Oldenburg. Sporting the Gibraltar cuff title, but unsure of the regiment. Either Füsilier-Regiment 73 or Infanterie-Regiment 79.