Rolex Explorer II watches

The Rolex Explorer II is the brand's steel tool watch for cave explorers, who lose track of day and night far from daylight. Rolex introduced it in 1971 as a companion to the original Explorer rather than a replacement. Its fixed bezel is marked with 24 hours, and an extra hand, orange on the first model, circles the dial once a day so the wearer can tell 3 a.m. from 3 p.m.

The first reference, the 1655, used that hand only as a day-and-night indicator. With the 16550 of 1985 the 24-hour hand became independently settable, which turned the Explorer II into a true GMT watch that can show a second time zone, and a white dial, known as the Polar, joined the black.

The 16570 carried the design on in a 40 mm, 11 mm steel case with a sapphire crystal, black or white dial, on calibre 3185 and later 3186. Its dials split by lume: early ones use tritium and carry a T marking beside SWISS at the bottom, while later ones switched to LumiNova and then Super-LumiNova and read SWISS MADE. That is the difference between the Tritium and Superluminova versions of the 16570, in both black and white.

In 2011 the 216570 grew to 42 mm, brought back the orange 24-hour hand of the 1971 original, enlarged the hands and markers and moved to calibre 3187 with Rolex's blue-glowing Chromalight lume. The 226570, released for the model's 50th anniversary in 2021, keeps the 42 mm size but has a slightly thinner case and slimmer lugs, black-coated hands and markers on the white dial, and calibre 3285, which runs for about 70 hours.