A fluted rim throws light back down onto the dial, and nacre is the one material that does something with it. Reference 278274 is the 31mm Datejust in a combination of stainless steel and white gold with a fluted bezel, and this configuration carries a white mother-of-pearl dial with diamond markers in solid white gold settings and no numerals, on the Oyster bracelet. A ring of angled polished facets standing above the crystal does not only send light outward. Some of it goes inward and downward across the face, arriving at angles the wearer is not looking from, and on a lacquered dial that contributes nothing because a lacquer returns light the same way regardless of where it came from. Nacre does not work that way.
The shell produces its appearance by interference rather than by reflection, its color arising from the layered structure of the material rather than from any pigment, so what it shows depends on the direction light reaches it as much as on the direction it is viewed from. A fluted bezel feeds it light from a constantly changing set of angles as the wrist moves, and the dial responds by shifting through pale pinks, greens and blues more actively than it would under a plain rim. The set-bezel version of this reference does something different, since colorless stones scatter light broadly rather than directing it, and the shell there runs its own range with less prompting. Neither is better and they are genuinely different watches. The diamond markers sit in white gold settings that sit close in value to both the stones and the ground, so the mounts nearly disappear and the markers read as bare points of light. Nacre is cut from shell, so no two of these dials carry the same banding. The Oyster bracelet is three broad flat links, brushed across the top with polished flanks, closing on a concealed clasp. The case is polished on the flanks and brushed across the lug tops, the lugs are short relative to the case, and every gold element is solid rather than plated.
The watch does one thing beyond telling the time. The date changes instantaneously at midnight rather than creeping through the hours around it, the function the Datejust introduced in 1945 and the one the model takes its name from. With no numerals anywhere the marker ring runs unbroken except at three, and a single aperture is as much as a ring arranged this way can absorb before it stops reading as one, which at 31mm is the tightest that constraint gets. The disc is matched to the dial, though matching a printed surface to a material that changes as the wrist moves is approximate at best, and the window sits slightly brighter than the shell at some angles and slightly duller at others. The window and its lens together take up proportionally more of a 31mm dial than of any larger case in the range, so on this configuration the date is the largest feature on the face and the only one with a straight edge. The Cyclops lens, fitted to the model since 1953, enlarges the numeral roughly two and a half times. 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 fifty-five hours, the figure the smaller cases carry rather than the longer one fitted to the 36mm, and a stop-seconds function allows the watch to be set against a reference rather than approximately. The crown screws down and the bracelet closes flush against the case.
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 that has always been the model's central size. Rolex registered the name for its steel and gold construction in 1933. The fluting began as a functional device, giving a tool purchase to screw the bezel down onto the case, and is now cut and polished purely for the way it catches light, which is what makes a white gold rim necessary on a case that is otherwise mostly steel, since the flutes need a metal that holds a crisp edge. Nacre entered the model long after either and has stayed at the decorated end of it, appearing on gem-set dials far more often than on plain ones, and it is never dyed, so what is on the dial is what the shell carried. Supply is the constraint rather than demand, since shell of the right thickness and clarity is finite and the yield after cutting is low. Each blank is sorted before it is cut, and the material appears on comparatively few references as a result. That scarcity is not a marketing position, it is a supply fact, and it is the reason nacre dials tend to be specified rather than stumbled upon.
The buyer for this wants a dial that is never the same twice and has chosen the rim that interacts with it rather than the one that sits above it. That is a subtle preference and most people arrive at it without being able to name it, having simply found that the fluted version looked more alive on the wrist. Every example differs, so anyone with a preference about the banding needs to see the individual watch rather than order the configuration, and photographs are close to useless because a still image freezes a surface whose entire character is movement. The Oyster is the flatter and more structural of the two bracelets and keeps the watch calm below the case. Nacre is thin and cannot be repaired or matched, so a damaged dial means a replacement carrying different banding rather than a restored original, and the flutes hold dust in their grooves in a way a smooth rim does not.
