Nothing on this dial is at a maximum, which is unusual and is the point of it. Reference 278243 is the 31mm Datejust in a combination of stainless steel and yellow gold with a domed yellow gold bezel, and this configuration carries an olive green dial set with diamonds and applied Roman numerals, on the Oyster bracelet. Olive is the only ground the reference offers that is both a color and a mid-tone, so the diamonds get moderate contrast rather than the maximum a dark dial gives them, and the numerals get moderate contrast rather than the strong separation they achieve against white. Every element is legible and none of them dominates.
That balance is difficult to arrange deliberately and easy to arrive at by accident, and the difference shows in how the dial is built. The lacquer is applied in several thin coats to keep the tone even across a curved surface, opaque and holding one value regardless of angle, and olive sits at the mid-point of the model's tonal range, neither dark enough to read as a neutral nor pale enough to read as a pastel. It also contains enough brown to meet a warm metal partway rather than opposing it, which matters more on yellow gold than on any other case Rolex builds, since yellow is the warmest metal in the range and a genuinely cool green would fight it. Against that ground the diamonds read as markers first and stones second, which is the reverse of how they behave on the dark grey dial built on this same reference. The Roman numerals are applied yellow gold and faceted, drawn for this case size rather than scaled from a larger one, and a full sequence occupies a considerable share of a 31mm surface before anything is set into it, so this dial is carrying two marker systems and a color at once. Steel and yellow gold is the most visible two-metal pairing Rolex makes, since yellow gold sits nowhere near steel in color and every junction between them reads as a clear boundary. The steel forms the case and the outer bracelet links while the gold takes the domed bezel, the crown, the bracelet center rows and the numerals, and the gold is solid rather than plated or capped. The bracelet is the Oyster, three broad flat links brushed across the top with polished flanks, tapering toward the clasp so the weight sits forward on the wrist. The date at three displaces the numeral that would otherwise sit there, on a disc matched to the dial.
Rolex matches the date disc to the dial rather than leaving a paler window in a colored surface, which decides whether the aperture belongs to the watch or interrupts it, and a single aperture is what allows a full Roman sequence to fit at all, since a second would leave no room for twelve numerals on a dial already carrying stones. The Cyclops lens above it has been part of the Datejust since 1953 and magnifies the date roughly two and a half times, which makes a small window readable without enlarging it and unbalancing the dial. The date changes instantaneously at midnight rather than creeping through the surrounding hour, the feature the Datejust introduced in 1945 and the one it takes its name from. Correction runs through the winding crown without moving the hands, and nothing the watch asks for requires a tool. The movement is self-winding with a power reserve of approximately 55 hours, an engineering result on a movement built to fit a 31mm case rather than a figure carried down the range, since a smaller barrel has less room to store energy and a proportionally smaller rotor gathers less of it. The rotor winds in both directions rather than only one, which lets a movement this size keep itself running on the wrist movement of an ordinary day. The crown screws down against the case, and the Oyster closes with a concealed clasp folded away inside the links.
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 original, which makes it the size for buyers who find one too small and the other too large. The 278000 generation replaced the 178000 series in 2018 with a revised case and bracelet. Rolex registered the name for its steel and gold construction in 1933, on the reasoning that steel supplies the structure and gold supplies the color. Green reached the Rolex catalogue broadly over the past decade and came to this model later than most colors, which is why the olive configurations still read as current where champagne has settled into the range. Within the generation, 278243 is the steel and yellow gold reference with a domed bezel. Olive green is one of three grounds here built in two set arrangements, alongside dark grey and silver, so each of the three holds four of the twenty-two rows where every other ground holds two. Olive green is never offered plain on this reference, which makes the stones a condition of the ground rather than a choice a buyer makes on it.
The buyer for this wants a set dial that is not organized around its stones. On the grey and silver versions the diamonds are either the brightest thing present or the only thing moving, and here they sit inside a composition where the color, the numerals and the stones each carry roughly equal weight, which produces a considerably more even watch. That evenness is either the appeal or the objection, since a buyer who wants a gem-set dial to look set will find this one understated. Buyers who have looked at all three gem-set Roman grounds on the reference generally arrive here when they want the color to survive the setting. It is the least emphatic gem-set dial on the reference and the one that holds together best under inspection. Six of the eight grounds here arrive set, and only champagne and white are ever offered plain on the reference.
