Hans Wilsdorf loves exploits, as evidenced by the Rolex watches that have equipped many adventurers. He designed and manufactured the Explorer I for Sir Edmund Hillary who decided to climb Mount Everest, "the roof of the world", at an altitude of 8,848 m. Designed to withstand all kinds of challenges, it is robust, reliable, readable and precise. It raises the brand to the rank of iconic myth-maker: a true legend is born, and the manufacturer strikes hard with this historic model.

Then Rolex launched production of the Explorer II in 1971 with the reference 1655. Instead of presenting an improved version of the Explorer I, a brand new model was introduced. A 24-hour steel bezel with a 24-hour scale allows the explorer working underground, mainly speleologists, to distinguish between day and night. For better legibility, there is a central orange 24h indicator hand which Italian dealers call "freccione", from Freccia meaning arrow, and which is most probably a legacy of the taste for extravagant colours of the 1970s. Typical of the 1655 reference, the steel bezel is engraved and enamelled 24 hours with " thin " Arabic numerals.