Of the five solid gold references at this size, only two carry a dark shell dial and both of them are yellow. Everose and white gold do not build the ground at all, and neither does any case above or below 31mm; black mother-of-pearl exists on six references in total, every one of them yellow and every one at this single diameter. Reference 278288RBR is the 31mm Datejust in yellow gold, carrying a bezel set with diamonds, and this configuration pairs a black mother-of-pearl dial set with twelve diamonds in gold settings, with no numerals, and a President bracelet. It is the narrowest ground the reference carries.
The case is solid yellow gold and the bezel is set all the way round in place of flutes. The dial is a dark shell, and it works in the opposite direction from the white one. Nacre produces color by refraction, and on a pale slice that yields a bright surface with color moving through it; on a dark slice most of the light is absorbed and what returns is a narrow flash of green, blue or bronze appearing at some angles and not at others. The dial looks black most of the time and is not black at all. Twelve round diamonds sit at the hours in gold settings matched to the case, and outside them the rim carries a second ring in solid metal. That outer ring is the brighter of the two by a wide margin, because the bezel stones sit against gold while the dial stones sit against a ground absorbing nearly everything that reaches it. What results is a watch with a bright edge, a dark middle and twelve small fixed points inside the dark. The President bracelet is semi-circular three-piece links in the same gold, rounded across their width, and it is the only bracelet the reference offers. Because the bracelet, the case, the rim and the mounts are one metal, the shell is the only surface on the watch that is not gold or diamond, and it is also the only one whose appearance was not decided in advance.
Hours, minutes, running seconds and a date advancing in one step at midnight. The self-winding movement in the 31mm case holds roughly fifty-five hours of running time, matching the 28mm references rather than the 36mm ones. Beyond that the watch does nothing, and the dial is read by position alone, because a diamond in a gold mount says nothing about the hour it marks. On this ground the twelve settings do more work than anywhere else on the reference. A dark shell surface gives an applied marker very little to sit against and a printed one almost nothing, so the stones are not decoration so much as the only reliable structure the dial has. Take them away and the watch would be close to unreadable in anything but direct light, which is presumably why the ground is never built plain. No shell dial in the current range is built unset, in either color, which separates the material from every other ground the model uses. The date window at three is the one break in the ring, and against black it is the highest contrast inside the crystal, higher than the diamonds themselves. With a set rim outside, the watch therefore has three levels of brightness working at once: the bezel, the date disc and the twelve stones, arranged in that order and separated by a ground returning almost nothing. That is an unusual hierarchy for a dress watch and it is why this configuration reads darker than its specification suggests. A list of components would put it among the most heavily decorated watches the reference builds, and on the wrist it is not.
Black mother-of-pearl is the most restricted ground the range currently builds. It exists at 31mm only, on six references, and it comes one way, with twelve settings and no numerals. There is no black shell in the 28mm cases, none at 36mm or 40mm, and no version with the oversized six that this reference builds on three other grounds. The six references carrying it are the same six that carry champagne and olive green, which is to say the yellow ones, and only two of those six are solid gold. Within this reference it is one of ten configurations set with diamonds and one of two whose appearance cannot be reproduced, the other being the white shell. It is also one of two confined to this diameter, alongside the red gradient dial. The three solid gold references with set rims at this size carry nine, nine and thirteen grounds and share only three of them; the black shell is one of the four this yellow reference holds alone. Champagne, the set champagne and olive green are the other three, which places the dark shell in company that is otherwise entirely warm. Eight grounds are built at this reference and black mother-of-pearl is one of six offered only with stones, taking diamond hour markers in gold settings rather than the large Roman six that three grounds here carry.
This is the configuration that gives up the most in a photograph and recovers the most in person. A dark shell dial photographs as a black dial, which understates it, and the color separating it from black appears only at angles a listing image rarely catches. Under a set rim that understatement goes further, since the stones on the bezel are the first thing any photograph records and the dial becomes a dark disc behind them. In person the balance is different: the shell opens as the wrist turns and the watch has more happening on it than the picture suggests. Anyone who wants the material to be obvious should take the white version on this same reference, where the figuring reads in any light. Anyone who wants a dark ground that behaves the same way every time should take the dark grey. And anyone who wants this dial without a second ring of stones should take 278278, where it sits under flutes.
