Rolex Explorer II 16570 ‘Polar' 40MM 1997

Rolex Explorer II 16570: The 40 mm Dual-Time Tool Watch Built for the Dark

Origins of the Explorer II Line

Rolex introduced the Explorer II in 1971 to assist spelunkers and polar researchers who struggle with day-night cues in low-light environments. The fixed 24-hour bezel, paired with a dedicated arrow hand, provided an intuitive AM/PM indicator that the original Explorer lacked. The first reference 1655, nicknamed “Freccione” for its large orange hand, set the template. In 1985 Rolex launched the transitional 16550 with a larger case, sapphire crystal and independent hour-hand adjustment, bridging classic and modern design language. Reference 16570 followed soon after, refining legibility, reliability and wearer comfort without abandoning the tool-watch ethos that defines the family.

Case and Bezel Architecture

The 16570 shares the 40 mm Oyster case profile common to contemporary Submariner and GMT-Master models, yet the silhouette feels leaner thanks to slab flanks free of crown guards. Rolex machines the case from corrosion-resistant 904L Oystersteel, then pressure-tests each watch to 100 m of water resistance. A fixed stainless-steel bezel carries engraved 24-hour numerals filled with gloss black lacquer. Unlike a rotatable GMT-Master insert, the solid bezel eliminates accidental movement during subterranean mapping or Arctic traverses, making time-offset reading fast and fool-proof. A signed Twinlock crown secures via twin O-rings and screws flush against the case, sheltering the calibre from shock and moisture.

Dial Variants and Hands

Rolex offered two dial colours: classic gloss black with white text and the now-iconic “Polar” matte white option with stark black surrounds. Both dials feature applied white-gold hour markers—triangles at 12, batons at 6 and 9, and circles for the rest—each filled with tritium lume. This 16570 carries its factory-original tritium dial, identifiable by the “SWISS – T < 25” footer at six o’clock. Tritium fills the applied white-gold hour markers—triangle at 12, batons at 6 and 9, and circular plots elsewhere—plus the Mercedes hour, sword minute and lollipop seconds hands. When freshly charged the lume glows a soft green, but over decades it mellows to a creamy patina that subtly warms the otherwise high-contrast layout. The red 24-hour hand ends in a luminous triangle that tracks the fixed 24-hour bezel, offering an instant day-night reference. A cyclops-equipped sapphire crystal magnifies the date by 2.5×, rounding out the watch’s legibility package without compromising its tool-watch aesthetic.

Calibre 3185 Dual-Time Movement

Inside the Explorer II 16570 beats Rolex’s calibre 3185, an automatic movement with 31 jewels and a 48-hour power reserve. The balance wheel oscillates at 28 800 vph, regulated by Microstella screws for fine adjustment and protected by Rolex’s patented Paraflex shock absorbers. Crucially, the movement enables independent local-hour setting in one-hour jumps without stopping the seconds or disturbing the 24-hour hand, allowing rapid time-zone changes while preserving accuracy. Each calibre receives COSC certification before casing, then endures Rolex’s own −2/+2 seconds-per-day inspection after final assembly, labelled “Superlative Chronometer” on the dial.

Bracelet, Clasp and On-Wrist Behaviour

Rolex pairs the watch with the three-link Oyster bracelet in solid 904L steel, reference 78790. The wide flat centre links sit flush against the tapering outer links, brushing matching the case lugs while polished flanks catch ambient light. Hollow end links nestle between pierced lugs, securing via 2 mm spring bars that facilitate fast strap swaps. Removable screws in the links simplify micro-sizing, while the Fliplock clasp offers a stamped safety latch and three micro-adjust holes for seasonal wrist changes. The complete steel assembly weighs roughly 135 g and distributes mass evenly across the wrist, aided by the watch’s moderate 12 mm thickness.

Luminous Evolution and Legibility

On dim cave walls, lume performance can be the difference between navigational certainty and disorientation. Early tritium plots like on this watch glow warm green when charged but fade to creamy hues over decades, developing attractive patina that collectors appreciate visually if not functionally. When Swiss regulators tightened tritium limits, Rolex shifted to non-radioactive Luminova, announcing the change with the dial signature “SWISS” at the six-o’clock line. A further update to Super-Luminova, indicated by “SWISS MADE,” offered brighter initial emission and longer after-glow. Regardless of formulation, the glossy piano-black surrounds on Polar dials and mirror-polished edges on black dials maximise contrast against the hands, ensuring at-a-glance clarity whatever the lighting.

Practical Dual-Time Operation

The Explorer II’s fixed bezel may appear limiting next to a rotatable GMT, yet the independent hour hand provides seamless adaptation in the field. Travellers set the red 24-hour hand to home time against the bezel, then adjust the local hour hand in one-hour detents via the crown. The date wheel advances forward or backward as the local hour passes midnight, a rare convenience among dual-time watches of the period. Scientists wintering in polar outposts often use the 24-hour hand for Coordinated Universal Time to align communication windows, leaving the conventional hour hand for station routines. Underground, speleologists simply treat the bezel as a day-night reference, preventing disorientation after long stretches without sunlight.

Dial Printing and Font Nuances

All Explorer II 16570 dials show five lines of text: coronet and “ROLEX” below 12, then “OYSTER PERPETUAL DATE,” “EXPLORER II” in signature serif font, and “SUPERLATIVE CHRONOMETER OFFICIALLY CERTIFIED” arching above 6. Early black-dial prints can appear off-white under loupe due to age, while Polar dials resist colour shift, maintaining crisp noir text against stark enamel. The red 24-hour hand on both versions fades faintly toward pink as the pigment’s epoxy binder oxidises, an aesthetic quirk that marks real-world wear.

Case Details and Production Transitions

Rolex retained lug-hole cases throughout this production phase, a detail prized by strap-swappers and field users seeking fast bar removal with a simple tool. The satin finish on the lug tops and case flanks sidesteps glare in bright snowfields or cave entrances. A narrow polished bevel edges each lug, capturing ambient light and easing the transition between brushed and polished surfaces. Slightly domed sapphire preserves the tool-watch silhouette without sacrificing impact resistance. Across the reference’s run, bezel numerals remain sharply engraved, unlike the painted aluminium inserts found on other sports models, granting near-permanent legibility and scratch resilience.

Role within the Rolex Line-up

While Submariner and GMT-Master share broader commercial profiles, the Explorer II addresses a niche yet vital audience that navigates prolonged darkness. Its classic 40 mm footprint accommodates a thicker GMT gear-train than the time-only Explorer while avoiding the rotating components of a diver’s bezel, resulting in a simpler external architecture. This watch quietly underpins the professional range, demonstrating Rolex’s ability to tailor core technology—Twinlock crown, Oystersteel, chronometer rating—to specialised tasks without over-complicating the design.

Field Reliability and Environmental Tests

Each finished Explorer II endures temperature cycling from −20 °C to +45 °C, salt-spray baths, and impact loads up to 5 000 g. Rolex’s corrosion chambers simulate decades of perspiration and seawater exposure, critical for steel that may confront humid tropical caves one month and dry alpine passages the next. The solid-end-link upgrade adopted later in the production run further bolstered bracelet rigidity, though the hollow-end-link version under discussion still provides ample structural integrity thanks to its robust rolled-steel construction.

Pop-Culture and Real-World Appearances

Beyond subterranean labs and polar huts, the 16570 found favour among airline pilots, mountain guides and photojournalists—anyone needing dual-time capability inside a low-profile case immune to reflection glare. Its discreet proportions fit neatly under winter gloves and flight jackets alike, while the high-contrast Polar dial photographs well under harsh flash, earning features in adventure magazines throughout the late 1990s and early 2000s.

Design Endurance and Contemporary Appeal

Although subsequent Explorer II references expanded to 42 mm and added Chromalight lume, the original 40 mm form retains universal wearability, especially on smaller wrists. The watch avoids flashy ceramics or maxi indices, instead relying on subtle updates—sapphire, 3185 calibre, higher-grade steel—to offer long-term robustness without altering the austere aesthetic established in the early 1970s. Its discreet, fixed-bezel outline also sidesteps the quick visual cues associated with dive or pilot watches, lending a degree of anonymity prized by journalists and security personnel working in volatile regions.

Final Thoughts

The Rolex Explorer II 16570 distils the core mission of the Explorer line—unwavering timekeeping in lightless environments—into a balanced 40 mm package. A fixed 24-hour bezel, independent hour-hand adjustment and durable calibre 3185 create a dual-time instrument that operates as effectively on a cave survey as it does crossing time zones at altitude. Through moderate case dimensions, crisp dial layouts and a corrosion-resistant Oystersteel build, the watch exemplifies purposeful design evolution, delivering clarity and reliability without superfluous ornament. A perfect tool watch.

• The case & bracelet both remain in great condition, hairlines visible around both sides of the case.
• Bracelet in great condition with some hairlines present.

• Dial & hands flawless
• Dial & hands forming light patina.