White nacre takes a stronger warm cast in yellow gold than in any other case Rolex builds. Reference 278243 is the 31mm Datejust in a combination of stainless steel and yellow gold with a domed yellow gold bezel, and this configuration carries a white mother-of-pearl dial set with diamond markers, on the Oyster bracelet. Nacre reports whatever surrounds it, and yellow gold is the warmest metal in the range, so the pale greens and pinks that surface as the wrist turns are pushed further toward gold here than the same disc would show in steel, white gold or even Everose. It is the least neutral reading of the material available.
Whether that is desirable depends on what the buyer wants nacre to be. The material is the lining a mollusc deposits inside its shell, laid down in microscopic layers over years, and the color travelling across a finished dial comes from those layers refracting light rather than from any pigment, so a surrounding metal does not tint the dial so much as bias which of its own colors come forward. Cut thin and mounted over a solid base plate, the disc keeps the orientation it had in the shell, which is why every example carries a different pattern and no two of these watches are identical, and how thickly the nacre is laid over that base governs how much depth the dial appears to have. Rolex grades the discs before fitting and rejects a high proportion, since a band falling in the wrong place can leave a marker or the date window sitting where the material shows no depth, and a flawed disc cannot be corrected but only discarded. The markers stand slightly proud of the surface and their height is what keeps them legible against a ground that is never a consistent brightness. Steel and yellow gold is the most visible two-metal pairing Rolex makes, and here the steel forms the case and the outer bracelet links while the gold takes the domed bezel, the crown, the bracelet center rows and the marker settings. The bracelet is the Oyster, three broad flat links brushed across the top with polished flanks. The date sits at three under the Cyclops lens with the aperture cut directly 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 finished 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.
Cutting a window into nacre without fracturing the disc is a genuine constraint and part of why the material appears on some references and not others. The Cyclops lens above the aperture has been part of the Datejust since 1953 and magnifies the date roughly two and a half times, and on a low-contrast ground like this one it does more work than elsewhere, since the printed date sits against a background whose brightness changes as the wrist moves. A single aperture also keeps the marker ring uninterrupted, since a second would break a pattern depending on continuity. The date changes instantaneously at midnight rather than creeping through the surrounding hour, the feature the Datejust introduced in 1945 and the one it takes its name from. Correction runs through the winding crown without moving the hands, and nothing the watch asks for requires a tool. The movement is self-winding with a power reserve of approximately 55 hours, an engineering result on a movement built to fit a 31mm case rather than a figure carried down the range. The rotor winds in both directions rather than only one. The crown screws down against the case, and the Oyster closes with a concealed clasp folded away inside the links. Hand winding runs through the same crown with no separate position to learn.
The Datejust arrived in 1945 as the first self-winding wristwatch to show the date in a window, and the 31mm case sits between the 28mm Lady-Datejust and the 36mm original. The 278000 generation replaced the 178000 series in 2018 with a revised case and bracelet. 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. Nacre came to the model much later than the metal combination and has stayed, largely because it does something no lacquer or cut stone can, and it has outlasted most of the decorative treatments Rolex has tried. Within the generation, 278243 is the steel and yellow gold reference with a domed bezel. Two-tone fell out of favor across the industry through the 2000s and returned over the past decade, and the Datejust carried it continuously. White mother-of-pearl is one of six set grounds on this reference and one of three built in a single arrangement, alongside champagne and black shell, while dark grey, olive green and silver are each offered in two arrangements instead, which gives those three four of the twenty-two rows apiece and leaves the rest with two.
The collector this suits wants nacre that belongs to the watch rather than one that reports itself. The white gold references give the cooler and more literal reading, showing the material's own colors with nothing pushing them, and this is the opposite, filtering everything through the warmest metal in the range so the dial and the case agree throughout. It is also the configuration where no two examples are alike, and buyers who care about owning a particular watch rather than a particular reference are drawn to that. It photographs least accurately of anything here, since a still image fixes one state of a surface that does not hold still. Anyone buying unseen should expect the watch to differ from its photographs rather than merely to exceed them. Eighteen of the reference's twenty-two rows carry stones on the dial, and shell is never offered plain among them in any configuration.
