Everything optical about this watch happens inside the crystal, which is not true of the version with stones on the rim. Reference 278274 is the 31mm Datejust in a combination of stainless steel and white gold with a fluted bezel, and this configuration carries a white mother-of-pearl dial with diamond markers in solid white gold settings and no numerals, on the Jubilee bracelet. A fluted rim is polished metal cut into facets, and metal reflects. Nacre refracts, producing color out of the layered structure of the shell rather than out of pigment, and the diamonds on the dial refract as well. So the only two materials on this watch that make color rather than merely returning it are both under the sapphire, and the entire optical event is contained.
That containment is what the set-bezel version of this reference gives up. Put stones at the rim and the watch has refraction inside and outside the crystal, and the eye stops distinguishing between them. Here the boundary is clean: reflective metal above and around, refractive materials within. It is a quieter arrangement and a more coherent one, and it is the reason the fluted rim suits nacre better than most people expect from a specification sheet. The markers sit in white gold settings close in value to both the stones and the ground, so the mounts nearly vanish and the ring reads as bare points on a shifting surface. Nacre is cut from shell, so no two dials carry the same banding, and at 31mm a smaller cut samples less of the material, which means broader bands and slower shifts rather than a finer version of the same pattern. The Jubilee runs five-piece links, three polished rows down the middle flanked by brushed outer rows, closing on a concealed clasp folded into the links. The case is polished on the flanks and brushed across the lug tops, and every gold element is solid rather than plated. The lugs are short relative to the case at this diameter, which keeps a 31mm watch from looking stubby, and the bracelet tapers continuously so the widest point of the whole piece is the bezel.
The watch does one thing beyond telling the time. The date changes instantaneously at midnight rather than creeping through the hours around it, the function the Datejust introduced in 1945 and the one the model takes its name from. With no numerals on the face the aperture at three is the only element on the dial with a straight edge, and against a material that has no straight lines anywhere in it that opening reads more strongly than it would on a lacquered ground. The disc is matched to the dial, which on a shifting material can only ever be approximate. The window and its lens together take up proportionally more of a 31mm dial than of any larger case in the range. The Cyclops lens, fitted to the model since 1953, enlarges the numeral roughly two and a half times. 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 fifty-five hours, the figure the smaller cases carry rather than the longer one fitted to the 36mm, so the calendar survives a weekend off the wrist and returns still correct. A stop-seconds function allows the time to be set precisely. The crown screws down and the bracelet closes flush against the case.
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 that has always been the model's central size. Rolex registered the name for its steel and gold construction in 1933. The fluting began as a functional device, giving a tool purchase to screw the bezel down onto the case, and is now cut and polished purely for the way it catches light. The Jubilee was designed for this model in 1945 and changes character with the diameter more than the Oyster does, becoming finer and more jewelry-like as the case shrinks, so at 31mm it is close to the most decorative form the bracelet takes. Pairing it with a shell dial and a fluted rim produces a watch where three surfaces are working at three different scales, the coarse natural banding of the dial, the regular facets of the bezel and the fine repeated links of the bracelet, with nothing on it competing at the same grain. That separation of scales is easier to achieve on a small case than a large one, since at 36mm the dial has enough area for the shell to show several bands and the distinction between the coarse and fine elements begins to close.
The buyer for this wants the interesting part of the watch to be the part they are looking at. That sounds obvious and it is not how most decorated watches are arranged, since the rim is usually the element carrying the decoration and the dial supports it. Here the order is reversed, and the fluted bezel is doing a supporting job, defining the edge and feeding light inward while the shell does the work. Buyers arrive here from the set-bezel reference having decided stones outside the crystal competed with the dial, and from the lacquered grounds having wanted a material rather than a color. Nacre is thin and cannot be repaired or matched, so a damaged dial means a replacement carrying different banding, the gold is solid rather than plated, and the flutes hold dust in their grooves in a way a smooth rim does not. Neither is a real drawback and both are worth knowing before rather than after, since a shell dial and a fluted rim are the two components on this watch that reward being looked after.
