An No.2C originally factory painted grey, over painted black with FAP to the front,First Aid Party.
It could also stand for First Aid Post too, but later in the war to dispel confusion these were marked 1st Aid Post.
Both shell & liner are dated 1940, & I think both made by BMB. The chin strap is an Mk.2A stamped with an M, being made of magnetic materials & so would not get mixed with straps for an Mk2 No.1 helmet (military issue).
The cotton twill on the inside of the liner has a nice ink stamp, probably an quality control stamp.