what does OPFB stand for on WW2 NFS helmet

[boris14]

Have a WW2 National Fire Service helmet. Ealing district. Has OPFB stencilled on front. Does anyone know what this stands for?

[bert_h]

Guessing ... Outer Perimeter Fire Brigade?

[EDDIE51]

The FB is virtually sure to be Fire Brigade. OP is probably the initials of the place / town/ area where the brigade is based.

[stewey]

Since Ealing is, and probably was during WW2, considered to be an "outer" borough of London, I would think that bert_h is on the right track.