Interestingly enough Michiel, I know of two more such helmets here in NZ. A friend has one with the names of soldiers inside the helmet much like yours with place names. Most were KIA, the owner brought the helmet home to Christchurch and it eventually came into a private collection direct from the family. I believe the owner was an officer also, and the second Im aware of is in a small museum at Collingwood in, Golden Bay. Again this is in the South Island, this helmet has the names and places listed on the exterior of the helmet and belonged to a local. Collingwood and Golden Bay in general are quite isolated parts of NZ, and would have been extremely isolated around the Great War period.
Very interesting to see a third as the two I have been privileged to examine are very interesting snapshots in time indeed.