Thanks for the feedback, t'other David. The lack of uranium is covered in my book, Chance Expressions, but as these ashtrays were originally produced before the war, then it is reasonable to assume they date pre-war rather than the 1950s when they may have already been discontinued.
If Stephen Pollock-Hill or Nigel stumble across this thread I'm sure they can comment re. Nazeing's output, but I doubt if any items were produced with uranium after WWII: I believe it was many decades before uranium was used again in British glass, but it would be nice to nail that particular point for dating purposes.
P.S. If the ashtrays were floating then, as a sub-mariner, I would be very worried! :24: