This is an original finger plate with a built in tube to fit a GPO dial 30 as used on original trimphones. It is a complete assemly including printed plate, reflector, tube and screws.
The tritium tube originally made the dial glow, but these tubes have lost their glow over the years as the half life of the tritium they contain is so short.
Even when new, radiation from these tubes was negligable and no more than normal background radiation that is all around us. They are now even less radioactive as they have lost their glow.
I have only ever seen two of these rare items as spare parts and we currently have one for sale.