Rolex Cosmograph Daytona 6240

The 6240’s short life is best understood as Rolex testing a sealed chronograph in real time. Around 1965 the reference appears as a steel Cosmograph Daytona that looks familiar at a glance, three registers, acrylic crystal, tachymeter on the bezel, but feels different when you handle it. The chronograph pushers no longer sit as simple pump tubes. They screw down, like the crown, turning the case into the first Daytona designed around the Oyster idea.

Early examples underline how transitional the project was. Christie’s and Phillips document watches with non-Oyster dials, including small “floating Daytona” dials associated with ref. 6239, fitted into the new screw-down case. The reason Rolex did this is not documented in factory material, but auction scholarship consistently reads it as pragmatic reuse of existing dial stock while the new configuration was being introduced.

Hardware evolves quickly. The earliest screw-down pushers are the ribbed “Millerighe” type, with fine vertical grooves that catch the light around the pusher cap. A specialist guide places these in an early serial band and notes that from roughly mid-1966 the pushers shift to a smooth cylindrical form. This change is independent of dial text, which is why a correct 6240 can pair early or later pushers with different dial layouts.

Meanwhile the movements progress within the same Valjoux 72-based family. Millenary documents 72B confined to 1965, then 722 through most of the run, followed by 722-1 in the last circa two years. These are refinements rather than reinventions, improvements in balance, shock protection, and regulation rather than a new complication or display.

The dial story is where the reference’s identity is most debated and most collectible. Hodinkee notes that many mid-serial examples are best known for omitting both “Oyster” and “Daytona,” the so-called “Solo” look, with T SWISS T at 6. Later, examples appear with “ROLEX OYSTER COSMOGRAPH” on the top line, aligning the wording with the screw-down hardware. Sigma-signed dials have been observed on some 6240s, but they sit in a less accepted category, largely because sigma is associated with the early 1970s while 6240 production is generally placed in the 1965–1969 band.

One zoomed-out truth emerges from all of this: the Daytona that now reads as a fixed template was still being assembled as a concept in the mid-1960s. The 6240 captures that moment, when the same reference can carry leftover pump-pusher-era dial language, prototype-like pushers, and a late-run Oyster signature, all while staying within a four-year arc that ends as the 6263 and 6265 generation takes over.

Ref. 6240 only makes sense when it is framed by the two watches it overlaps and the one it foreshadows. Ref. 6239 shows the original pump-pusher, metal-bezel Daytona that 6240 did not replace so much as challenge. Ref. 6241 is the near-twin in look, the same black acrylic bezel idea but kept on pump pushers. Ref. 6263 is the long-form answer to the 6240 experiment, carrying the screw-down, black-bezel formula forward for years rather than seasons.

Buying a Rolex 6240 is less about finding a clean example than finding a coherent one, because so many valuable components can be swapped: pushers, bezel insert, and dials all trade independently of the case. The reference’s short c. 1965–1969 run means even small mismatches can move a watch from convincing to compromised. The safest purchases are those whose dial generation, pusher type, and movement designation make sense together for the mid-to-late 1960s, and whose most fragile parts, especially the acrylic bezel, have not been replaced.

Living with a correct 6240 is the pleasure of a purposeful 1960s chronograph that still wears compact at around 37 mm, yet feels unusually engineered for its era because every control screws down. It is the Daytona that rewards looking closely, not because it hides secrets, but because it documents Rolex’s own learning curve in steel, acrylic, and ink.