Explorer 6350

The first reference with “Explorer” on every dial and the first Explorer chronometerChronometerA watch or movement certified for timekeeping precision under a defined testing standard. The applicable certification depends on its maker and period; it is not the same as a chronograph., marked “Officially Certified ChronometerChronometerA watch or movement certified for timekeeping precision under a defined testing standard. The applicable certification depends on its maker and period; it is not the same as a chronograph.”. Most known cases are stamped IV.53 inside the back, though assembly seems to have continued for some years.