A little late maybe, however
Around WW2 this was :-
SIGNALLING LAMP, TYPE B (Stores Ref. 5A/2334)
globes (special prefocus cap) were either
Lamp, filament, 12 volts, 30 watts" (Stores Ref. 5A/2339) which became 5L/2339 or
Lamp, filament, 24 volts, 30 watts" (Stares Ref. 5A/2340 which became 5L/2340
Lamp, filament, In early models a spare filament lamp is carried in a clip inside the carrying case, but in
later models the spare filament lamp is carried in a clip in the lamp body. . It is important to keep the
reflector, bulb, and front cover free from steam or moisture, as this produces diffusion and scattering
of the beam and renders the lamp inefficient.
The cover (11) (Stores Ref. 5A/2335) consists of an annular steel plate in which is fitted
a disc of clear glass. If necessary a cover (Stores Ref. 5A/2336) containing a green disc or a cover
(Stores Ref. 5A/2337) containing a red disc, may be fitted, these discs may be of glass or synthetic
resin material.
5A/2338 Box For complete lamp
5A/2368 Box For coloured fronts
5E/1611 Cable, connecting Complete with Plug, 2-pin, type A (5C/959)
Yours seems to be missing the rubber eye-piece (1)
Cheers,
Bobby