Pilot’s Chronograph Doppelchronograph 3713

Successor to the 3711 with a flat sapphire crystalSapphire crystalA watch glass made from transparent synthetic sapphire, valued for its resistance to scratching.; most have Super-LumiNovaLumiNova and Super-LumiNovaTrade names for luminous coatings that absorb light and release it in darkness. These non-radioactive materials differ from radium- and tritium-based lume., but early ones still use tritiumTritiumA radioactive luminous-paint ingredient used on many vintage watches after radium. On RAF IWC Mark 11 replacement dials, an encircled T identified the tritium specification..