The stones on the bezel are never all lit at once and the stones on the dial always are. Reference 278341RBR is the 31mm Datejust in a combination of stainless steel and Everose gold with a domed bezel set with diamonds, and this configuration carries a chocolate dial with a full Roman sequence whose large VI is set with diamonds, on the Oyster bracelet. The bezel is a curved band rather than a flat ring, so its stones sit at continuously changing angles and only a section of them catches a given light source at any moment. The dial stones are gathered into one numeral on a flat surface, so they behave as a single unit and light together or not at all. The same stone, the same metal holding it, and two entirely different behaviors.
A domed bezel set with stones is not a flat ring, and that changes what it does with light. On a flat or a fluted bezel every stone sits in the same plane and the ring lights more or less evenly. On a dome the outer stones tilt away from the viewer while the inner ones face nearly forward, so a single light source reaches only part of the band at a time and the bright arc travels around the bezel as the wrist turns. The effect is closer to a rotating highlight than to a static circle of points. The stones are set into the case metal itself rather than into mounts laid onto it, which is what allows the curve to stay continuous. Everose is the brand's own rose gold, alloyed with platinum so the tone holds instead of drifting toward yellow over decades, and it gives the stones a faintly warm surround that a cool metal would not. The chocolate dial beneath is an opaque lacquer laid in thin coats to hold an even tone across its own curve, pitched to the alloy, since the same color in a cool case would read close to black. Steel takes the case body and the outer bracelet links while Everose takes the bezel, the crown, the bracelet center rows, the numerals and the hands, all of it solid rather than plated. The Oyster bracelet is three broad flat links, brushed across the top with polished flanks, closing on a concealed clasp. The metal between the settings stays polished, so the bezel returns light from the gold as well as from the stones and never reads as a dark band between bright points.
The watch does one thing beyond telling the time. The date changes instantaneously at midnight rather than creeping through the hours around it, which is the function the Datejust introduced in 1945 and the one it takes its name from. Its disc is matched to the chocolate ground rather than left pale, so the aperture does not open a bright gap in a dark surface, and the frame around it is drawn for a 31mm dial rather than reduced from a wider one, which keeps it from pressing against the numerals at its shoulders. The Cyclops lens above the window has been fitted to the model since 1953 and enlarges the numeral roughly two and a half times, which on a dark dial is the difference between a date that is read and one that is worked out. Correction runs through the winding crown at a dedicated position and leaves the hands where they are. The movement is self-winding with a power reserve of approximately 55 hours, built for a case this narrow rather than carried down from a wider one, since a smaller barrel stores less energy and a lighter rotor takes in less of it from the same arm. The crown screws down against the case.
The Datejust has been in production since 1945, when it became the first self-winding wristwatch to show the date through a window on the dial. The 31mm case sits between the 28mm Lady-Datejust and the 36mm original, and 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 everything the eye takes in. Everose arrived in 2005, and the brown dials now associated with it followed rather than preceded it. Within the generation, 278341RBR is the steel and Everose reference with a diamond-set domed bezel, and it sits directly alongside 278241, which is the same watch with a plain dome. Those two are worth understanding as a pair. On the plain-bezel reference a single set numeral is the only decoration the watch has and carries the whole weight of it. Here the same numeral is a secondary element, and specifying it becomes a decision about balance rather than about whether to decorate at all. Chocolate is the only ground here built in two set arrangements, which gives it four of the fourteen set rows.
The buyer for this wants the case to do the announcing and the dial to stay legible. A gem-set bezel is visible from across a room and a Roman sequence with one set numeral is not, so the watch reads as decorated at distance and as ordinary in the hand, which is the order most people find comfortable. Chocolate supports it by absorbing rather than returning light, keeping the dial quiet underneath a rim that is not. The Oyster bracelet holds the same line, three broad links built for daily wear rather than for occasions. What is worth seeing in person is the dome. Photographs light a bezel evenly and show a uniform ring of stones, which is not what it does on a wrist, where only part of it is ever bright at once. Buyers who came from the plain-bezel reference wanting more usually stop here rather than continuing to a fully set dial, and buyers who came down from the set marker rings tend to say the numerals were what they had missed.
