One surface on this watch returns light constantly and the other returns it only occasionally. 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 black mother-of-pearl dial with diamond markers in gold settings and no numerals, on the Jubilee bracelet. The Jubilee throws light back at short intervals along the whole length of the wrist without pause. The dial does the opposite. It holds close to black through most of its range, then breaks into color for a moment and goes quiet again. Wearing the two together produces a watch whose bracelet never changes and whose face keeps interrupting itself, and the pairing is either the most interesting thing the reference offers or the most restless, depending entirely on who is wearing it.
Black nacre is the least consistent ground on the reference and the one that repays close attention most. It is the inner lining of a shell, built up in fine layers that split light as it passes through rather than reflecting it off the top, which is why the color it shows is a function of angle rather than a property of the material. Held still it reads as near-black with a faint sheen. Moved, it releases green and blue and occasionally violet, and then loses them again. No two blanks are alike, because the shell they were cut from was not made to a specification. Rolex sets the diamond markers into solid gold surrounds kept low and tight against that surface, partly because a raised setting crowds the hands on a 31mm dial and partly because a low one lets the ground run right up to the edge of each stone. The Jubilee then supplies the constant. Its five-piece links run roughly twice the component count of the Oyster across the same width, with polished gold rows down the middle and brushed steel to either side, so the wrist stays lit while the dial comes and goes. The case is steel, and the gold at the bezel, crown, bracelet center rows, marker settings and hands is solid throughout.
For a watch carrying this much surface, the mechanism behind it is deliberately narrow. It shows the time and the date, and the date changes instantaneously at midnight instead of creeping through the hours around it, the function the Datejust introduced in 1945 and was named for. The disc is matched to the black ground so the window reads as part of the dial rather than a hole in it, and the aperture frame is drawn for this diameter rather than reduced from a wider one, which keeps it clear of the markers at its shoulders. The Cyclops lens above it has been fitted to the model since 1953 and enlarges the numeral roughly two and a half times, which matters here because there is no printed numeral anywhere else on the dial to set a reading distance by. Correction runs through the winding crown at a dedicated position and leaves the hands untouched. The movement is self-winding with a power reserve of approximately 55 hours, designed around this case width rather than adapted down to it, since a smaller barrel holds less and a smaller rotor collects less from the same motion. The crown screws down, and the Jubilee closes on a concealed clasp that disappears into the links.
The Jubilee was introduced alongside the Datejust in 1945 and built specifically for it, which is why the two read as original together in a way the bracelet does not on anything else in the range. The model was the first self-winding wristwatch to display the date in a window and has been produced without interruption since. The 31mm case falls between the 28mm Lady-Datejust and the 36mm original, and the 278000 generation took over from the 178000 series in 2018 with a revised case and bracelet. Rolex registered the name for its steel and gold construction in 1933. Nacre dials have been in the catalogue for decades without ever becoming a standard option, because the material limits how many can be made. A shell yields only a small area of even, usable stock, and dark nacre of consistent tone is harder to find than pale. Within the generation, 278343RBR is the steel and yellow gold reference with the diamond-set domed bezel, and the black nacre ground appears on it only with set markers. A nacre dial also cannot be replaced later with a matching one, since the original was never one of a set to begin with. Rolex does not publish how many nacre dials it makes in a given year, and no reliable count exists outside the factory.
This is the most active configuration the reference offers, in the sense that more of it is doing something at any given moment than on any other version. The bracelet is lit continuously, the bezel holds a fixed ring, and the dial moves in and out of color underneath both. Whether that reads as lively or as unsettled depends on the wearer, and it is not a watch that resolves on paper. Buyers who like it tend to describe the same thing, which is that the dial gives them a reason to look at the watch when there is no reason to check the time. Those who do not like it usually want a face that stays put, and the Oyster version of this same dial exists for exactly that preference. Trying both is the only way to settle it, since neither photographs in a way that tells anyone much. What is not in question is that the two bright elements are consistent with each other, since the bezel stones and the marker stones are the same cut in the same metal.
