This is the one diameter where the ground offers no choice at all. A white dial comes with Roman numerals and nothing else on all seventeen references at 31mm, where at 36mm and 41mm the same ground gains an applied-marker version on some of the cases and not others. So a white Datejust 31 is a single dial across the entire size, and the only variables left are the metal, the rim and the bracelet, which is the smallest set of decisions the ground presents at any diameter. Reference 278271 is the 31mm Datejust in a combination of stainless steel and Everose gold, carrying a fluted bezel, and this configuration pairs that dial with an Oyster bracelet.
The case is thirty-one millimeters in steel with an Everose gold bezel, crown and center links, and the rim is fluted, cut into a repeating series of angled facets rather than polished into a single band. The dial is a flat white holding one value at every angle, and Roman numerals in gold stand at the hours. This is the highest-contrast unset combination the reference builds: white and gold separate completely in any light, where the chocolate and rose grounds this reference also carries sit close to the case in tone and the slate declines to engage with it. Only white sets a cool bright surface directly against warm metal with nothing in between, which is why it is the ground a buyer chooses when the case is meant to be the warm element rather than the dial. A Roman numeral holds more metal in the same footprint than an applied baton would, so a full set puts a considerable amount of warm material on an otherwise cool face, and ten characters at this diameter occupy a large share of the surface, which is what stops the dial reading as a foreign object dropped into a rose gold case. The Oyster is built from three-piece links with the gold as one continuous center line between broad flat sections of brushed steel, so the wrist stays largely cool and the warm metal is concentrated in a rim, a crown and a stripe, which on a white dial produces a watch that reads as steel with gold on it rather than as a two-metal object. A three-piece link is also stiffer across its width than the five-piece alternative, so the bracelet holds a fixed curve and the watch sits squarer on the wrist rather than following it.
Hours, minutes, running seconds and a date changing in one step at midnight rather than easing into the following day. The self-winding movement in the 31mm case holds roughly fifty-five hours of running time, matching the 28mm references rather than the 36mm and 41mm ones, which run a larger movement of their own. The date sits at three under a magnifying lens and takes a position that would otherwise hold a numeral, so the Roman set runs to ten characters rather than eleven; ten still name their own positions and nothing about the layout depends on the missing one. On a white ground the window is less disruptive than on any other dial the reference builds, since a white disc against a white ground is nearly continuous with it and only the frame marks the break. At thirty-one millimeters the characters are also close to the smallest the model prints them, and a pale ground is what keeps the set from crowding, since it gives each one maximum separation. The fifty-five hours the movement holds are worth stating plainly, since the two smaller cases share a movement of their own and a buyer moving up from this size to 36mm gains fifteen hours without changing anything else about the watch.
White carries no metal preference anywhere in the range. It reaches eight case sizes from 28mm to 44mm, on cases in steel, in all three two-metal combinations and in solid gold in every tone, which is more than any other ground the catalogue offers by a wide margin, and at 31mm it is the only dial built on all seventeen references. Everything else this reference builds is narrower than that: chocolate and rose belong to Everose, slate at this size belongs to Everose, and the shell and the silver reach widely without reaching everything. Within the reference white is one of nine grounds across twenty-two rows, and the reference itself is the fluted one of four steel and Everose cases at this size, which is more rims than any metal gets at 36mm or 41mm, alongside the domed 278241, the domed set 278341RBR and the fully set 278381RBR, all four carrying the same nine grounds. Counting both bracelets, a plain white dial in this alloy at this size therefore exists in eight watches, and only the rim and the bracelet separate them. Seven grounds are built at this reference and white is the only one the catalogue never offers with stones on the dial. Rose and slate appear both plain and set, while aubergine, chocolate, silver and mother-of-pearl exist in set form alone.
This is the plainest watch the reference builds and the one that gives the case the most to do. No stones, no color, no matched tone, just a white ground with gold characters inside a two-metal watch, on the bracelet that shows the least gold. For a buyer who wants an Everose Datejust that reads as formal rather than as warm, it is the most direct answer on the reference, and the contrast makes it the easiest of its dials to read. That combination, maximum legibility and minimum incident, is what has kept the configuration in the catalogue essentially unchanged for as long as the model has existed. Anyone who wants the dial to agree with the case should take the rose or the chocolate. Anyone who wants more warmth at the wrist should take the Jubilee. And anyone who wants an applied-marker white will have to change size, since at this diameter no reference builds one in any metal.
