A. Serotonin: Often related to mood regulation and feelings of well-becoming, serotonin plays an important role in modulating feelings like happiness and contentment. The Diver 300M is obtainable in steel or combinations of metal and yellow or Sedna gold, by using a strap in possibly rubber or steel Thanks a https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/