This is a NEW OLD STOCK (NOS) British Prefocus (BPF) or P36 base (12V, 45W) TUNGSTEN driving/spotlamp bulb. It is correct for SLR576, SLR700 and Spot Ranger lamps.
These have a vertical filament, which throws a conical beam, correct for a driving lamp, although they fit in foglamps as well.
Our bulbs come from several manufacturers, including LUCAS, Stanley, etc.
Reproduction 185 bulbs are no longer manufactured. Large suppliers provide reproduction 323 foglamp bulbs in place of 185 bulbs, which fit but throw a different shaped beam and are not correct. We have a large supply of these correct driving lamp bulbs.