This Oyster Perpetual Explorer II in Oystersteel with an Oyster bracelet features a black dial with an arrow-shaped 24-hour hand and hour markers with a chromalight Display.  
 
Its highly legible dial, extremely resistant Oystersteel and waterproofness have made it the watch for the extremes.
 
The Explorer II features a date display, an additional orange 24-hour hand and a fixed bezel with 24-hour graduations, enabling day to be distinguished from night. It became the watch of choice for speleologists, volcanologists and polar explorers. Its hour markers and hands feature a highly-legible Chromalight display with long-lasting blue luminescence.
 
BRAND Rolex
MODEL Oyster Perpetual  Explorer II - 216570
GENDER: Male (42mm)
MOVEMENT: Automatic, Rolex Calibre 3187
MODEL CASE Oyster, 42 mm, Oystersteel OYSTER ARCHITECTURE Monobloc middle case, screw-down case back and winding crown DIAMETER 42 mm
MATERIAL Oystersteel
BEZEL Fixed, 24-hour graduated
WINDING CROWN Screw-down, Twinlock double waterproofness system
CRYSTAL Scratch-resistant sapphire, Cyclops lens over the date
WATER RESISTANCE Waterproof to 100 metres / 330 feet
MOVEMENT Perpetual, mechanical, self-winding, GMT function
CALIBRE 3285, Manufacture Rolex
PRECISION -2/+2 sec/day, after casing
FUNCTIONS Centre hour, minute and seconds hands. 24-hour display. Second time zone with independent rapid-setting of the hour hand. Instantaneous date. Stop-seconds for precise time setting
OSCILLATOR Paramagnetic blue Parachrom hairspring. High-performance Paraflex shock absorbers WINDING Bidirectional self-winding via Perpetual rotor
POWER RESERVE Approximately 40 hours
BOX/PAPERS:  Rolex box, Rolex booklet, hang tag, wallet and Rolex card 
CONDITIONS: Pre-owned, Excellent