OO/EM/P4 Stencil Indicator with the word 'OFF' used for signalling in platforms.
An 'OFF' indicator is used at places where the driver may be unable to see the main signal in a platform (for example if it is curved or very long). When the word OFF lights up, it is clear to proceed.
There is a section behind the stencil, large enough for a Surface Mount LED, I would recomend a pre-soldered version, similar to
this. Designed using original tehnical drawing direct from Unipart Dorman (who suppy these to Network Rail) and its includes detail sush as the sighting tube. If you do intend to add an LED, I recommend painting te stencil black to prevent light bleed.