Strange Belgian M1917A1 "Kelly" helmet liner

[Estonian]

X.B -Manufacturer Xavier Buisset Vilvoorde

F.P -what means ???

[emileverbunt]

F.P. probably stands for "Force Publique".
This was the military organisation in the then Belgian Congo. Consisted out of native rank and file, officered by Belgians.

Cheers,
Emile