Sized at 31 mm, the Datejust 31 ref. 278243-0018 is built around a Yellow Rolesor case — Rolex's combination of Oystersteel and yellow gold — featuring a domed bezel, scratch-resistant sapphire crystal with a Cyclops lens over the date, and a screw-down crown equipped with the Twinlock double waterproofness system. The Oyster architecture includes a monobloc middle case and screw-down case back, delivering water resistance to 100 metres / 330 feet.
The dark grey dial is set with diamonds, with the large VI position accented by 11 diamonds and Roman numeral hour markers throughout. A matching Yellow Rolesor Jubilee bracelet with five-piece links secures via a concealed folding Crownclasp, carrying the same two-material combination across the entire piece.
Inside runs the Calibre 2236, a perpetual mechanical self-winding movement bearing Manufacture Rolex origins. It features a Syloxi silicon hairspring with patented geometry, Paraflex shock absorbers, bidirectional winding via a Perpetual rotor, a power reserve of approximately 55 hours, and a precision rating of -2/+2 seconds per day after casing. The movement holds Superlative Chronometer certification, reflecting both COSC testing and Rolex's own post-casing standards.
