This is the only dial on the reference that is as bright as the stones set into it. Reference 278343RBR is the 31mm Datejust in a combination of stainless steel and yellow gold with a domed bezel set with diamonds, and this configuration carries a white mother-of-pearl dial with diamond markers in gold settings and no numerals, on the Oyster bracelet. Every other ground offered here gives the marker stones something to separate from, whether a dark lacquer, a saturated color or a warm metallic tone. White nacre does not. It returns about as much light as the diamonds sitting on it, and it moves while doing so. What locates the markers instead is the gold around them, which turns a decorative element into a working one and quietly changes what the settings are there for.
The gold settings stop doing decorative work here and start doing something the dial actually needs. Each stone sits in a solid gold surround, and against a pale, shifting ground those warm rings are the only fixed reference the eye has for where the hours are. Take them away and the markers would come and go with the nacre underneath them. That is why this dial reads as ordered rather than diffuse. The nacre itself is the inner lining of a shell, cut thin and backed so the tone stays even, and it produces color by splitting light as it passes through the layers rather than reflecting it off the top. In a case of steel and yellow gold it picks up a warm cast it would never take in a cool one, so the dial sits closer to cream than to true white through most of its range and shows pink and pale green at the edges of it. Rolex keeps the settings low against the surface, since a raised marker on a 31mm dial interferes with the hands before it adds anything to the look. The case is steel with gold at the bezel, crown, bracelet center rows, marker settings and hands, all of it solid rather than plated. The Oyster bracelet is three broad flat links, brushed on top with polished flanks, closing on a concealed clasp folded inside them.
The date window does more here than it does anywhere else on the reference, because it supplies the only dark element on the dial. Its disc is matched to the nacre rather than left plain, and the numeral printed on it is the single fixed, high-contrast mark the eye can settle on. The date changes instantaneously at midnight instead of drifting through the hours around it, the function the Datejust introduced in 1945 and takes its name from. Above the aperture the Cyclops lens, fitted to the model since 1953, enlarges that numeral roughly two and a half times, which on a dial with no printed markers is the difference between a date that is read and one that is worked out. The frame around the window is drawn for a 31mm dial rather than reduced from a wider one, so it does not push against the markers at its shoulders. Correction runs through the winding crown at a dedicated position and leaves the hands alone. The movement is self-winding with a power reserve of approximately 55 hours, built for a case this narrow rather than carried down from a larger one, since both the barrel and the rotor are smaller and each does proportionally less. The crown screws down against the case. Nothing the watch asks for in normal use happens anywhere other than at the crown.
The Datejust has been made continuously since 1945, when it became the first self-winding wristwatch to show the date through a window on the dial. 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. Rolex registered the name for its steel and gold construction in 1933, on the reasoning that steel supplies the structure and gold supplies everything visible. White nacre has been the more widely offered of the two shell dials across the range, appearing on more references and in more case metals than the dark version, which is a matter of supply rather than taste, since pale shell of an even tone is easier to obtain in usable sizes. It is also the version that changes most with the case around it, reading cool in white gold and platinum and warm in yellow and Everose, so a single catalogue description covers dials that look meaningfully different from one another. Rolex does not distinguish between them in its own naming, which leaves the burden of describing a specific example with the seller rather than the catalogue. Within the generation, 278343RBR is the steel and yellow gold reference with a diamond-set domed bezel, and the white nacre ground is offered on it only with set markers rather than with a Roman sequence.
The buyer for this wants the brightest watch the reference can be built as and accepts that legibility comes second to it. In practice the dial is read by position rather than by contrast, which most owners stop noticing within a week and a few never stop noticing at all. It is the one thing to be sure of before committing. What the configuration gives back is a watch with no dark element anywhere on it except the date, which is difficult at this size and impossible to arrange with a lacquer dial. The Oyster bracelet keeps the wrist plain and lets the head carry all of it, and three broad links are also the more practical choice for a watch that is going to be worn rather than set aside. Buyers usually arrive here from the silver gem-set dial wanting the same brightness with movement in it, and a smaller number arrive from the black nacre version having decided they wanted the material and not the darkness.
