The Rolex Datejust 31 (reference 278240) is a self-winding wristwatch with a 31 mm case in Oystersteel and 18k white gold. Rolex calls this steel-and-gold combination Rolesor. The date shows in a window at 3 o'clock under a Cyclops lens.
The silver dial has applied index hour markers, and a polished domed bezel surrounds it. The watch is fitted with an Oyster bracelet with three-piece links.
It runs on the self-winding Rolex caliber 2236, with a power reserve of about 55 hours. It is certified as a Superlative Chronometer, with accuracy of −2/+2 seconds per day once cased. A screw-down crown and a sapphire crystal give it water resistance to 100 meters.
- Reference
- 278240
- Case size
- 31 mm
- Case material
- Oystersteel and 18k white gold
- Bezel
- Domed
- Dial
- Silver index dial with applied index hour markers
- Crystal
- Sapphire
- Crown
- Screw-down
- Movement
- Rolex caliber 2236, mechanical, self-winding
- Power reserve
- About 55 hours
- Accuracy
- Superlative Chronometer, −2/+2 seconds per day once cased
- Functions
- Hours, minutes, seconds, date
- Bracelet
- Oyster, three-piece links
- Water resistance
- 100 m / 330 ft