The Rolex Explorer II reference 216570 was introduced in 2011, forty years after the first Explorer II, and made until 2021, when the 226570 replaced it. Built for explorers, cavers and polar expeditions, where day and night can be hard to tell apart, it adds a 24-hour hand to the Explorer: read against the fixed, engraved 24-hour bezel, it shows whether it is day or night, or a second time zone.
This is the white-dial version collectors call the "Polar". The black-ringed hour markers and black hands stand out on the white dial, and the large orange arrow-tipped 24-hour hand recalls the very first Explorer II. The 42 mm Oystersteel case has a screw-down crown, a sapphire crystal with a Cyclops lens over the date and a solid screw-down caseback, and is water resistant to 100 metres (330 feet).
Inside is the self-winding Caliber 3187, a certified Superlative Chronometer with a Parachrom hairspring and Paraflex shock absorbers, with about 48 hours of power reserve. It is worn on an Oystersteel Oyster bracelet with an Oysterlock safety clasp and the Easylink comfort extension link.