Two rings of identical stones, and the ground is the only reason they look different. Reference 278343RBR is the 31mm Datejust in a combination of stainless steel and yellow gold with a domed bezel set with diamonds, and this configuration carries a dark grey dial set with diamond markers and no numerals at all, on the Oyster bracelet. The bezel stones sit on gold and the dial stones sit on dark lacquer, and with no numeral sequence between them the comparison is direct and unavoidable. It is the clearest demonstration on the reference of how much a background does to a diamond.
Everything else about the two sets is the same. Both are seated individually into recesses cut for them rather than dropped into preformed channels, both are graded for size so their rings read as even, and both use the same stones. The difference is entirely environmental. On the bezel each diamond has to separate from bright yellow gold and manages it partially, and on the dial each one separates from a matte dark ground completely, so the inner ring reads sharper and more distinct while the outer reads as a continuous band of brightness. That is not a flaw in either. A bezel is meant to frame and a marker is meant to be found, and the two grounds serve those different jobs correctly. Dark grey is the most neutral of the deep colors offered here, applied as an opaque lacquer in several thin coats so it stays even across a curved surface, and Rolex keeps the marker settings low and tight since a raised marker on a 31mm dial has little room before it starts to crowd the hands. Steel and yellow gold is the most visible two-metal pairing the brand makes, and here the steel forms the case and the outer bracelet links while the gold takes the bezel, the crown, the bracelet center rows and the marker settings. 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. The date sits at three under the Cyclops lens on a matched disc. Rolex also matches the height of the marker settings to the height of the date frame, so the dial reads as one plane with elements standing off it rather than as several plates at different levels, and the hands are polished yellow gold drawn for this case size rather than scaled from a larger one.
Rolex matches the date disc to the dial rather than leaving a paler window in a darker surface, and against a dark ground the magnified numeral carries as much contrast as a date display can be given. A single aperture also keeps the marker ring uninterrupted, since a second would break a pattern that depends on running continuously. The Cyclops lens above it has been part of the Datejust since 1953 and magnifies the date roughly two and a half times. 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 crown screws down against the case, and the Oyster closes with a concealed clasp folded away inside the links. A movement of this size gathers less from the same wrist movement than a larger one, so the watch does better worn daily than kept aside between outings.
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. Dark grey has appeared across several generations of the model without ever being the volume seller, and gem-set markers have been offered on it for most of that time. Within the generation, 278343RBR is the steel and yellow gold reference with a diamond-set domed bezel. Gem-set bezels are also serviced differently from gem-set dials, since a bezel can be reworked without opening the case and a dial cannot. Grey has stayed in the range far longer than most of the grounds introduced alongside it, and the gem-set versions have followed it throughout rather than appearing and being withdrawn. Dark grey is one of three grounds at this reference given two marker arrangements, with olive green and silver, and the diamond hour markers here are the treatment six of the seven grounds share.
The buyer for this gets the most legible gem-set dial the reference offers and pays for it with a bezel that reads softer than the dial does. Whether that matters depends on how the watch is looked at, since from any distance the bezel is what registers first and the dial resolves only closer in. Most people find that ordering natural. It is also the most straightforward configuration here to live with, since a matte lacquer shows no variation between examples and none over time, and on the Oyster the whole watch stays built for regular use rather than for occasions. Buyers who found the silver marker dial too diffuse arrive here and generally stop looking. Grey is never offered plain at this reference, so the comparison a buyer makes is between its two set arrangements rather than between a set and an unset face. Only champagne and white can be had without stones, and white alone is unset in every configuration.
