@Horlogerie excellent post earlier on re luming of watch hands coincided with a friend kindly giving me a gift of two old (his words) watches. 
At the base of the dial on the Rotary Sport watch is the letters 'Pm'.
As I had not seen this before (honestly) I proceeded to do a bit of research.
It appears to be the symbol for 'Premethium (Pm) 147' a radioactive isotope, sounds like something which an assassin would use to coat the tip of his umbrella. 
The questions, concerns it now raises for me are:
1. Is the watch intended for a Lady?
2. Will handling, wearing the watch hinder any future plans to become a donor?
3. Will it negate the need to switch the light on at night when emptying my bladder?
4. Has any other member come across this type of lume & was it's use common?
As yet I have not inspected the movement as it has literally just arrived but it will go to doctors for new crystal etc, after crimbo.
Any comments as always will be appreciated.
Alan
