The busiest bracelet Rolex fits to this model, under the least predictable dial it makes. Reference 278243 is the 31mm Datejust in a combination of stainless steel and yellow gold with a domed yellow gold bezel, and this configuration pairs a black mother-of-pearl dial set with diamond markers with the Jubilee bracelet. Five rows of alternating steel and yellow gold across the wrist, and above them a dark nacre disc that changes as it moves. Nothing on this watch holds still, which makes it the most restless configuration on the reference and the one that rewards being seen in person by the widest margin.
The Jubilee's five links across the width put yellow gold center rows between steel outer links, and because yellow gold sits nowhere near steel in color the alternation reads as a clear boundary between two materials rather than as a change in finish, so the bracelet is doing as much visually as the dial is. The gold is solid rather than plated or capped, which is why these bracelets survive decades of wear where most of the industry's two-tone watches do not. Nacre is the lining a mollusc deposits inside its shell, laid down in microscopic layers over years, and its color comes from those layers refracting light rather than from pigment, so a dark disc shows flashes of green and blue emerging from something close to black rather than the soft shimmer a pale disc gives. Every example carries a different pattern, and Rolex grades the discs before fitting and rejects a high proportion, since a band falling in the wrong place leaves a marker sitting where the material has no depth. Against the dark ground the diamond markers carry maximum contrast. The domed bezel above is smooth and unbroken, the quietest shape the model is offered with, which is the only element on the watch not competing for attention. The date sits at three under the Cyclops lens with the aperture cut into the nacre. The base beneath the disc is a solid plate, and how thickly the nacre is laid over it governs how much depth the dial appears to have, which is a second source of variation between examples on top of the banding itself. The hands are polished yellow gold and drawn for this case size rather than scaled from a larger one, kept narrow so they read as warm lines against a ground with no consistent background of its own. The bracelet also carries roughly twice the component count of the Oyster across the same width.
Cutting an aperture into nacre without fracturing the disc is a real constraint and one reason the material appears on some references and not others. The Cyclops lens above it has been part of the Datejust since 1953 and magnifies the date roughly two and a half times, which makes a small window readable without enlarging it and unbalancing the dial. A single aperture also keeps the marker ring uninterrupted, since a second would break a pattern that depends on running continuously. The date changes instantaneously at midnight rather than creeping through the surrounding hour, the feature the model introduced in 1945 and the reason it carries the name it does. Correction runs through the winding crown without advancing the hands, and nothing the watch asks for requires a tool. The movement is self-winding with a power reserve of approximately 55 hours, engineered into a movement built to fit a 31mm case rather than carried down from a larger one, since a smaller barrel stores less energy and a proportionally smaller rotor supplies less of it. The rotor winds in both directions rather than only one. The crown screws down against the case, and the Jubilee closes with a concealed clasp folded away inside the links. Correction takes seconds and requires no tool.
The Datejust arrived in 1945 as the first self-winding wristwatch to show the date in a window, and the Jubilee was introduced the same year for that watch, which makes it native to the model. The 31mm case sits between the 28mm Lady-Datejust and the 36mm original, and the 278000 generation replaced the 178000 series in 2018 with a revised case and bracelet. Nacre came to the model much later than the metal combination and has stayed, and the dark varieties are rarer than the pale ones since they are harder to source in a consistent grade. Two-tone fell out of favor across the industry through the 2000s and returned over the past decade, and the Datejust carried it continuously rather than dropping and reviving it. Within the generation, 278243 is the steel and yellow gold reference with a domed bezel. Rolex registered the name for its steel and gold construction in 1933, on the reasoning that steel supplies the structure and gold supplies the color, and the division has held unchanged since. Dark nacre also reached the two-metal references later than the pale variety, which is part of why it turns up less often than its presence in the catalogue would suggest.
This appeals to a buyer who wants the watch to be doing something everywhere. The Oyster version concentrates all the movement in the dial and leaves the wrist plain, and this one refuses that, giving the bracelet its own fine alternation of two clearly different metals so the object is active from the clasp to the crystal. Some people find that more than they want at 31mm and take the Oyster for exactly that reason, which means the pair attracts genuinely different buyers rather than the same one weighing options. It is also the more comfortable of the two, since more links across the same width follow a small wrist more closely. Anyone shopping the pair should expect to decide on how much activity they want below the lugs, since the dial is identical between them. Eighteen of the reference's twenty-two rows carry stones on the dial, and this is one of them.
