Honest John wrote
wrote

whatever those "t's" mean.

Those Ts simply refer to the luminous substance used in the watch to
make the hands and dots "glow in the dark". I believe the Ts stand
for Tritium, the amount of Tritium used is above a certain industry
established limit for this slightly radioactive substance.

Tritium is a radioactive isotope of hydrogen, the one after deuterium.

Unlikely that thats in a watch to make the hands glow.

Sort of like a "warning label". Ts are used on other watch, also.