Two things on this watch were selected rather than made, and only one of them was chosen for what it looks like. Reference 278341RBR is the 31mm Datejust in a combination of stainless steel and Everose 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. The diamonds were graded and picked to match one another so the bezel reads as an even band. The nacre was cut from a shell and could not be matched to anything, because the shell was never made to a specification and no two blanks come out alike. One selection was made to eliminate variation and the other could not eliminate it at all.
Nacre produces color by splitting light through fine layers rather than reflecting it off a surface, which is why what it shows depends on the angle and partly on what is reflecting into it. A warm case feeds it warm light. Against Everose the dial runs cream and pink where the same blank in a cool case would run closer to blue, so the ground reports the alloy as much as it reports itself. Outside the crystal the bezel does the opposite. Its stones are colorless and cut into a continuous polished surface, and because the bezel is a dome rather than a flat ring they sit at continuously varying angles, so only an arc of the band is lit at a time. That arc is predictable and repeats identically on every example Rolex builds. The dial does not. The marker settings are solid Everose kept low and tight against the surface, and on a ground with no reliable tone of its own they are what actually locates the hours, since the nacre gives the eye nothing fixed to measure from. Steel takes the case body and the outer bracelet links while Everose takes the bezel, the crown, the bracelet center rows, the marker settings and the hands, all of it solid rather than plated. The Oyster bracelet is three broad flat links, brushed across the top with polished flanks, closing on a concealed clasp.
With no numerals printed anywhere the date window supplies the only fixed dark mark on the face, and Rolex treats it accordingly. Its disc is matched to the nacre rather than left plain, which is the hardest match on the reference to make, since the surface it has to agree with changes color as well as brightness. The date changes instantaneously at midnight rather than creeping through the hours around it, the function the model introduced in 1945 and takes its name from. The frame around the aperture is drawn for a 31mm dial rather than reduced from a wider one, so it does not press against the markers at its shoulders, and the Cyclops lens above it, fitted to the model since 1953, enlarges the numeral roughly two and a half times. That magnification matters more here than on a printed dial, because there is no other character on the face to establish a reading distance by. Correction runs through the winding crown at a dedicated position and leaves the hands where they are. 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 wider one, since a smaller barrel stores less energy and a lighter rotor takes in less of it from the same arm. The crown screws down against the case.
The Datejust has been in production 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. Shell dials have been in the catalogue for decades without ever becoming a standard option, limited by how much even, usable material a single shell yields, and the pale version has always been easier to obtain than the dark. Everose arrived in 2005, and pairing nacre with it produced a dial that had existed for years but had never looked quite this way before, since the alloy feeds the material a light no earlier Rolex case metal could. Within the generation, 278341RBR is the steel and Everose reference with a diamond-set domed bezel, and 278241 offers the identical dial under a plain dome. Setting the bezel gives the nacre something fixed to be seen against, which is the one thing the plain reference cannot supply. Shell arrives set on this reference and is never offered plain.
The buyer for this is accepting that no two examples are the same and that a photograph will not settle the choice. Nacre has to be seen moving, and two of these on one counter can differ from each other more than two different dial colors would. That puts the weight on handling the specific watch rather than the specification, which is unusual for a Rolex and is the main thing to understand before ordering one. What the bezel adds is a reference point. Against a ring of graded stones that behave identically every time, the dial's variation becomes something a buyer can actually measure rather than simply notice, and most people find the nacre more interesting on this reference than on the plain one for exactly that reason. The Oyster bracelet keeps the wrist plain underneath and leaves the head as the only place anything is happening. Buyers arrive here from the silver dial wanting movement in the ground, and from the white lacquer wanting the same brightness with something going on inside it. Anyone comparing two of them should look at the bezels first, since those are identical, and let the dials speak for themselves.
