The Rolex GMT-Master has been in production for 21 consecutive years, from 1959 until 1980. In that period, there have been a few changes to the watch, however no major changes. The hour markers are in tritium and age over time, which causes the color to change from white to beige or sometimes even brownish. Collectors appreciate it when the hours markers are nice and equally discolored to beige tones, and prices rise accordingly. This Swiss vintage Rolex GMT-Master 1675 beauty is from 1966.