The Rolex Explorer II was introduced in 1971.
Rolex designed the Explorer II as a Professional tool watch for explorers, especially speleologists working underground where natural daylight could disappear for long periods. Its fixed 24-hour bezel and additional 24-hour hand let the wearer distinguish daytime from nighttime even when the surroundings made that impossible.
The first model was reference 1655. Its bright orange arrow-tipped 24-hour hand became the defining visual feature of the early Explorer II, and collectors later gave that hand the nickname “Freccione,” meaning “large arrow” in Italian. Unlike the standard Explorer, the Explorer II included a date display and used a fixed rather than rotating 24-hour bezel.
The model’s purpose explains why 1971 is the key date, even though later generations can make the timeline confusing. Reference 16550 followed in 1985, and reference 16570 arrived in 1989 with the calibre 3185. The modern Explorer II remains part of Rolex’s Professional collection and retains the 24-hour orientation concept.