Worth A Read In the mid 1950s, Rolex introduced the caliber 1030, their first complete in-house built and designed movement. This new movement required a new generation Explorer, leading to the introduction of the reference 6610 in 1956. The 6610 was slimmer than its predecessors, with a 36mm case design and a flatter caseback. The dials were all glossy black with gold text, and some rare versions had a depth rating. In 1963, Rolex introduced the Explorer 1016, one of the longest running sports watch references. Production ceased in 1989, but minor changes occurred, including the introduction of the caliber 1560, a chronometer-rated movement, and the 1570, which added a hacking feature. The 1016s were also rated to a slightly deeper depth rating at 100m. One of the biggest changes in the 1016's lifespan was the shift from Radium to tritium for luminous materials on the hands. The 1016 Explorer featured matte dials with text printed onto the dial surface. Towards the end of the 1980s, Rolex introduced the next generation Explorer, the reference 14720. This watch replaced acrylic crystal with scratch-resistant sapphire glass, giving it a more modern feel on the wrist. The dial replaced painted numerals with white gold numbers filled with luminous material, initially tritium, and then luminova for lume. The reference 114720 was introduced in 2000, powered by the 3000 series movement.
