Case
Case Size: 31 mm diameter
Case Material: Yellow Rolesor — combination of Oystersteel and 18 ct yellow gold
Case Architecture: Oyster, monobloc middle case
Water Resistance: 100 metres / 330 feet
Crown: Screw-down Twinlock winding crown with double waterproofness system
Caseback: Solid, screw-down Oyster caseback
Bezel: Fluted, in 18 ct yellow gold
Bezel
Type: Fluted, non-rotating bezel
Material: 18 ct yellow gold
The fluting is a signature Datejust design feature; it is not a Cerachrom 24-hour bezel.
Crystal
Type: Scratch-resistant sapphire crystal
Date Magnification: Cyclops lens over the date at 3 o’clock
Movement
Calibre: Rolex Calibre 2236
Type: Perpetual, mechanical, self-winding
Winding: Bidirectional self-winding via Perpetual rotor
Power Reserve: Approximately 55 hours
Functions:
Hours
Minutes
Central seconds
Instantaneous date with rapid setting
Stop-seconds for precise time setting
Accuracy: −2/+2 seconds per day, after casing
Oscillator / Balance
Hairspring: Syloxi hairspring in silicon with patented geometry
Shock Protection: High-performance Paraflex shock absorbers
Escapement: The official Rolex specification for reference 278273 does not list a Chronergy escapement or blue Parachrom hairspring.
Dial
The exact dial depends on the individual 278273 configuration/dial code. Rolex has offered this reference with various dial colors and configurations, including white, silver, dark grey, olive green, champagne and diamond-set versions.
For example, one official 278273 configuration has:
Dial: Olive green, gloss, sunray finish
Hour Markers: 18 ct yellow-gold Roman numerals, with some configurations featuring a diamond-set VI.
Hands
Hour Hand: Central hour hand
Minute Hand: Central minute hand
Seconds Hand: Central seconds hand
Bracelet
Reference 278273 is available with Rolex’s Yellow Rolesor bracelet configurations.
Oyster Bracelet:
Three-piece solid links
Oystersteel outer components with 18 ct yellow-gold center components
Folding Oysterclasp
Easylink 5 mm comfort extension link
Jubilee Bracelet:
Five-piece links
Yellow Rolesor construction
Depending on configuration, a concealed folding Crownclasp may be used
Certification
Certification: Superlative Chronometer
Certification Basis: Official chronometer certification (COSC) + Rolex certification after casing
Accuracy: −2/+2 seconds per day, after casing
International Warranty: 5 years