The 278273 is the Datejust 31 in Oystersteel and yellow gold, which Rolex calls Rolesor: the fluted bezel, the crown and the centre links of the Jubilee bracelet are in 18 ct yellow gold, the case and the other links in Oystersteel. The reference appeared in 2018 as the successor to the 178273, which was made from 2009 to 2018.
The Datejust dates from 1945 and was the first self-winding wristwatch with a date that changes in a window on the dial; the Cyclops lens over the date was added in the 1950s. At 31 mm the 278273 sits between the smaller ladies' sizes and the classic 36 mm. Inside works calibre 2236, which Rolex has used in the Datejust 31 since 2018, with a power reserve of about 55 hours. The watch is water-resistant to 100 metres. Dials range from champagne and silver to versions with diamond indices.
Gold is softer than steel, so on a pre-owned example we pay extra attention to the gold bezel and centre links, where scratches and polishing marks show sooner, to play in the bracelet and to the clasp. We also test the time and date functions and check the completeness of the set. Anyone looking for a larger Datejust will find it in the Datejust 41.
