Daytona Chronographs Calibers

In the 1960s, the most used and trusted chronograph movement of industrial production was VALJOUX, which had varying levels of quality. Staying with the company's philosophy and standards, Rolex chose the highest level of the movement available for its chronographs, in this case for its Daytonas.

Main characteristics of the Daytona chronographs calibers (calibers derived from the caliber 72 A):

  • caliber engraving on the plate on the hub sinking of the balance wheel
  • brand and jewels engraving on the chronographic bridge, in two versions:
    • in two lines (earlier models)
      • ROLEX GENEVE
      • 17 RUBIS
    • in five lines (more recent models):
      • MONTRES ROLEX S.A.
      • GENEVA SWISS
      • ADJ. TO 3 THREE POSITIONS
      • SEVENTEEN
      • 17 JEWELS
  • place of manufacturing engraving on the train wheel bridge:
    • SWISS MADE FABR. SUISSE
  • name brande engraving on the plate under the dial:
    • ROLEX GENEVE
 
 

Caliber 72A

Until 1987 all Rolex chronographs movements were based on the Valjoux caliber 72 B, personalised with modified structural specifications, such as the use of the two horizontal screw holders of the case and the introduction of the Rolex balance with the Microstella regulation system.

Caliber 72b or 722

The 72 B caliber evolved from the 72 A basic caliber and then was renamed 722. It was produced from 1960 to about 1967. This represents a transitional period characterised by the introduction of the Microstella regulation mechanism, which would replace the regulator of the basic caliber.

This movement is realised in the two versions with the engraved writings on two or five lines on the chronograph bridge.

The symbol ROW (Rolex Werke) can be found on the balance cock, indicating that the movement was made specifically by Rolex.

Caliber 722-1

The caliber 722-1 evolved from the caliber 72 B or 722 and is also based on caliber 72 A. It was produced from 1967 until about 1969.

It was realised with the text engraved on the chronograph bridge in the 2 or 5 line versions, and it is identical to the previous movement (72 B / 722), with the exception of the conveyor spring for hour recorder and relative screws. This modification was made by Rolex to resolve problems of force and leverage in the movement of the hour register. 

caliber 727

The caliber 727 is an evolution of caliber 722-1 and was also based on caliber 72 A. It fitted onto Daytona chronographs from 1969 to about 1987.

To further enhance performances, Rolex replaced the balance, which goes from 18,000 to 21,000 vibrations per hour, thus making it far more precise than the previous ones. This modification entailed the replacement of 15 components, screws, and relating clamps.

Rolex also eliminated the spring for protecting the hairspring present on calibers 72 B or 722 and 722-1, from which it was sometimes removed during repair work.