WW1 German M16 helmet reused by Bulgaria?

[battle gear]

I think this could be a WW1 era German Model 1916 shell that has been refurbed by the Bulgarians? the chin strap has been modified with swivel loops riveted in place, and the leather liner looks like the type Ive seen used in Czech or Bulgarian helmets, the leather chin strap also has a split for the chin as often seen on Bulgarian helmets, I think this could be a Cold war era reissue? or possibly used by Bulgarian Home Guard / Civil Defense?

also notice two small holes one on each side of helmet, I think those may have been for a different chin strap from another modification during it's life.

Also notice the large rounded liner rivets? they look the same as the type of rivets used on the Bulgarian M36A helmets.

What era / time frame would you say this helmet was still in use? the re-paint doesnt look very old?

[Kaikun2001]

This looks to be the case������