Mother-of-pearl is the only set dial in the Day-Date range that goes everywhere. Three grounds reach all four case metals and both case sizes, and the other two are white, which carries no stones at all, and the paved dial, which splits at 40mm and hands the cool metals a separately listed ground with sapphires in it. Only mother-of-pearl set with diamonds is offered in every metal at every size in one form. So a collector who wants a set dial and does not want the metal or the diameter deciding it for them has exactly one ground to work with, and this is the platinum version of it at the larger size.
The material is the inner layer of a mollusk, sliced thin and laid over a base rather than applied as a finish, built from stacked microscopic platelets that split light as it passes through them and returns. The ground never holds a value, drifting between white, cream and pale green as the wrist turns, and each slice carries a figure specific to the piece it came from. Platinum is the ideal case for it in one narrow respect: the metal reflects close to neutral and adds no tone of its own, so the shell shows what it actually is rather than what a warm case makes of it. At 40mm there is more of that surface, and the figure has room to run rather than being cropped by the openings. The markers are baguette-cut stones running the whole way around, identical in cut, length and orientation, laid flat rather than raised, returning light in broad planes from a single angle while the ground scatters it unevenly. Nothing accents six or nine. The case is 40mm with the flat wide lugs and low band the model uses throughout, the bezel is fluted, and the President bracelet closes it in polished three-piece links. The figure is also easier to appreciate at this diameter. Shell is cut from a curved shell and flattened, so the bands and swirls it carries run at whatever angle the slice caught, and on a small dial a strong figure can be cropped until only a fragment of it is visible. A wider dial holds more of the pattern intact, which is why two examples of this configuration differ from one another more obviously than two examples of the 36mm version do.
At the larger size the calendar takes proportionally less of the dial, which matters more on shell than on any other ground. Every opening cut into the material removes surface that was chosen for its figure, and the day arc at twelve is wide because the day is spelled out in full in words rather than shortened to three letters. At 36mm that arc consumes a substantial share of the slice; at 40mm the same arc sits inside a larger field and takes less of it, so more of the figure survives. Both openings are framed, since an unframed edge would show the laminate in section and a flat printed disc needs a firm boundary against a surface that will not hold one value for it to match. Both discs jump instantaneously at midnight rather than turning through the hour before, and the movement runs roughly seventy hours off a full wind. The date sits beneath a lens set into the crystal, and on shell that magnification does something particular. It holds a printed numeral perfectly still while the material immediately around the window keeps moving with the light, so the eye reads a fixed magnified character against a surround that will not settle. It is the only point on the dial where anything is held steady, and the contrast with everything else is part of why a shell dial reads as busier than it measures.
The marker arrangement is where the ground's reach ends, and at this size the decision has already been made. Mother-of-pearl is offered in two treatments at 36mm on every metal, one with hour markers set into gold surrounds and one with baguettes throughout; at 40mm the framed version does not exist and this is the only arrangement available. So a buyer choosing the larger case gives up a choice they would have had at the smaller one, without the two decisions being presented as connected. Thirteen grounds are offered on platinum at 40mm and only five cross to the smaller platinum case, mother-of-pearl among them with white, blue ombre and ice blue in both forms. Two references carry the roster, this one with a fluted bezel and 228396TBR with a set one. The three universal grounds are not equivalent at this size despite sharing the same reach. White is a manufactured finish and looks identical on every metal it is fitted to. The paved dial splits here, handing the cool metals a separately listed ground with sapphires. Mother-of-pearl alone arrives unchanged in every metal at both diameters, and it is the only one of the three that also takes on the tone of whatever surrounds it.
Shell on platinum under a fluted bezel is the most restrained way the model presents a set dial, and the combination is more considered than it first appears. Every element on the watch is cool and every element except the dial is fixed, so the shell is the only thing that moves, and it moves against surroundings that give it nothing to compete with. On a warm case the same dial would be arguing with the metal; on the set-bezel reference it would be arguing with a ring of stones. Here it has the watch to itself. For a collector who wants mother-of-pearl treated as a material rather than as decoration, and wants the case to stay out of the way while it does whatever the light asks of it, this configuration is the least crowded place in the range to put it. The larger case gives the material more room than any other configuration in the model does.
