Diamonds and nacre do the same thing to light, and putting them on the same dial should be a mistake. Both break light unpredictably rather than reflecting it in a fixed direction, and a marker that behaves like its own background usually disappears into it. Reference 278344RBR is the 31mm Datejust in a combination of stainless steel and white gold with a domed bezel set with diamonds, and this configuration carries a white mother-of-pearl dial with gem-set markers in white gold settings, on the Jubilee bracelet. What keeps it legible is height rather than contrast, since the settings raise the stones off the surface far enough that they cast a shadow the nacre cannot.
That is the whole engineering problem of a gem-set nacre dial, and it is solved in the mounting rather than in the stones. Rolex sets the markers in white gold settings raised slightly proud of the disc, and the shadow beneath each one is what registers before the diamond does, which is why the markers stay findable on a ground whose brightness is never consistent. The nacre itself 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. Every disc carries a different pattern, so no two of these watches are the same, and Rolex grades them before fitting and rejects a high proportion, since a band falling in the wrong place leaves a marker sitting where the material shows no depth. The case is a combination of stainless steel and white gold, the least visible two-metal pairing the brand makes, and the Jubilee contributes five links across the width with white gold center rows between steel outer links, where the two metals sit close enough in color that the alternation reads as a change of finish rather than of material. The date sits at three under the Cyclops lens with the aperture cut into the nacre. The height of the setting is also what keeps a marker findable when the nacre goes momentarily bright beneath it, since at that instant the stone and the ground are the same value and only the shadow separates them. Rolex keeps those settings low enough that they do not crowd the hands, which at 31mm is a tighter constraint than on a larger dial, and the hands themselves are polished white gold drawn short of the markers so they cross without appearing to touch them.
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 on a ground this low in contrast it earns that twice over, since the printed numeral sits against a background whose brightness changes as the watch moves. The date changes instantaneously at midnight rather than creeping through the surrounding hour, the feature the Datejust introduced in 1945 and the reason the model carries its name. A single window keeps the marker ring uninterrupted where a second would break a pattern depending on continuity. Correction runs through the winding crown without advancing the hands, hand winding uses the same crown, 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 inherited from a larger one. The crown screws down against the case, and the Jubilee closes with a concealed clasp folded away inside the links. Winding by hand runs through the same crown with no separate position to learn, and a movement of this size gathers less from the same wrist movement than a larger one, so the watch prefers regular wear to rotation. Correction takes seconds and requires no tool, which matters more on a watch intended for constant wear than the reserve figure itself does.
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. Steel and white gold is the quietest two-metal combination Rolex offers, and a diamond-set bezel covers most of the only surface where the second metal would be identifiable, so the bezel reads as diamonds rather than as gold with stones on it. Nacre joined the model much later and has outlasted most of the decorative treatments the brand has tried, appearing across several generations rather than arriving and leaving with one. Within the generation, 278344RBR is the steel and white gold reference with a diamond-set domed bezel. White gold is also considerably denser than steel, so the bezel here is noticeably heavier than a steel one of the same dimensions, and that weight is the one way the second metal announces itself on a reference where it cannot be seen. Rolex casts its own gold in a foundry on its premises, which is why it can hold an alloy to a consistent color across decades of production.
This appeals to a buyer who wants a watch that is entirely about light. Between the bezel, the markers, the nacre and a five-piece bracelet there is no surface anywhere on it that reflects in a simple direction, which produces something that never looks the same twice from any angle. That is either the most interesting configuration on the reference or the most restless, and buyers tend to know which within a few seconds. 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. It is also among the more difficult configurations to photograph, since a camera fixes both the nacre and the stones in one state and neither holds still, and examples consistently read differently in person rather than merely better. Anyone buying unseen should expect that, and anyone buying in person should expect to spend longer with it than with a lacquer dial.
