J Jkbenn02The common theory on this is lots of UV exposure (aka direct sunlight). Some people fade their inserts with bleach though. This process can easily go too far if you are not careful though.
J Jkbenn02The dials marked with a T should be only Tritium. After that they may be luminova.
J Jkbenn02Luminova (and more so SuperLuminova) far out glows tritium which by now probably doesn't glow much anymore. They stopped using Tritium primarily in the mid-90s.