Introduced in 1971, the Rolex Explorer II was developed as a specialist instrument for explorers working in environments where the distinction between day and night could become difficult to establish. Designed particularly with cave exploration in mind, the original ref. 1655 featured a fixed 24-hour bezel and a prominent orange hand that completed one revolution every 24 hours, allowing its wearer to distinguish between daytime and nighttime when natural light was unavailable. Unlike the GMT-Master, the earliest Explorer II did not offer independently adjustable hour hands, instead using its 24-hour indication as a practical extension of conventional timekeeping. This changed with the introduction of the ref. 16550 in 1985, which brought a new movement, redesigned dial and independently adjustable local hour hand. Its successor, the ref. 16570, arrived in 1989 and would remain a cornerstone of the Rolex professional collection for more than two decades.

Dating to 2000, this Explorer II ref. 16570 represents the mature evolution of the original concept, combining the familiar 40mm stainless steel Oyster case with a black dial and fixed 24-hour bezel. Its contrasting white hour markers and Mercedes-style hands provide excellent legibility, while the distinctive red 24-hour hand introduces a subtle touch of colour to the otherwise monochromatic design. By this period, the Explorer II had evolved into a versatile travel watch, with its independently adjustable local hour hand allowing the wearer to track a second time zone while retaining the original 24-hour functionality. The automatic Rolex calibre 3185 provides the mechanical foundation, while the solid-end-link Oyster bracelet reflects the gradual refinements introduced during the reference's lengthy production run.