Every element on this watch was manufactured except the dial, which was only chosen. Reference 278289RBR is the 31mm Datejust in solid white gold with a bezel set with diamonds, and this configuration pairs it with a white mother-of-pearl dial carrying gem-set markers in white gold settings, on the President bracelet. The case was machined, the bracelet was assembled, the stones were cut and set, and the nacre grew inside a shell over years without reference to any of it. Rolex's contribution to the dial is selection and cutting rather than making, which on a watch this precisely built is a genuine anomaly.
Nacre 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. Cut thin and mounted over a solid base plate, the disc keeps the orientation it had in the shell, so 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 at all. That rejection rate is the whole of the quality control available, because a flawed disc cannot be corrected, only discarded. The markers sit in raised white gold settings whose height keeps them legible against a ground that is never a consistent brightness. The case is solid white gold, uniform from the lugs through the bracelet and considerably denser than steel, and the bezel is set with diamonds. 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 a wider variation in the thickness of the nacre laid over it produces a second source of difference between examples on top of the banding itself. White nacre in a cool case also behaves differently from the same material in yellow or rose gold, where it takes a consistent warm cast, and here it reports only its own colors rather than reflecting the metal around it.
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 model 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. 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. A single aperture is also part of why the marker ring holds together, since a second would interrupt a pattern depending on continuity. 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. The crown screws down against the case, and the President closes with its clasp concealed within the links. Correction takes seconds and requires no tool. That display is shared by every ground this reference builds, ten in all, so the nacre changes nothing about how the watch is used.
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. Nacre came to the model much later than the metal and has stayed, largely because it does something no lacquer or cut stone can, which is change appearance continuously rather than simply catch light at an angle. It has also outlasted most of the decorative treatments Rolex has tried, appearing across several generations rather than arriving and leaving with one. The President bracelet was designed in 1956 for the Day-Date and appears here as a borrowing. Within the generation, 278289RBR is the solid white gold reference with a diamond-set bezel. Solid gold references are also built in far smaller numbers than the steel and two-metal ones, and the white gold versions in smaller numbers again. Rolex has never offered nacre across the whole catalogue, restricting it to references where the aperture can be cut without risking the disc, which is why it appears far less often than the material's popularity would suggest. On a solid gold reference the constraint is tighter still, since a fractured disc means a case already finished has to wait.
The collector this suits wants one element of the watch to be beyond anyone's control. Everything else here can be specified, repeated and matched, and the dial cannot, which means this particular example is the only one of itself in a way no lacquer configuration can claim. Buyers who care about owning a specific watch rather than a specific reference are drawn to nacre for exactly that reason. It also photographs least accurately of anything on the reference, because a still image fixes one state of a surface that does not hold still, so examples consistently read differently in person rather than merely better. It is worth handling before buying rather than after, since two examples can differ enough that someone who liked one may not like the next. Anyone buying unseen should expect the watch to differ from its photographs rather than merely to exceed them, and should treat any single image as one reading of several.
