Case material 18ct red gold   Case thickness 13.07mm   Case diameter 42.00mm   Water resistance 3.00 bar (approximately 30 meters)   Between shoulders 23.00mm  Sapphire crystals front and back with anti-reflective coating.

The case back removed.

Compression case back recto-verso.

Calibre 6639 

Winding Automatic   Calibre thickness 7.60mm   Calibre diameter 32.00mm   Power reserve 192 hours   Jewels 35   Components 303   Frequency 4 Hz / 28’800 A/h

The 6639 movement’s surface finish is a combination of Geneva stripes and hand angling. The rotor is finished with a gold insert with engine turning. These elements differentiate it from the 1315 calibre. The balance is in titanium and carries gold regulation adjustment screws

For additional technical information regarding the basic calibre refer to the Fifty Fathoms deconstruction here.

The rotor mass. During assembly and initial testing of the movement, a working mass is used and only replaced with the definitive mass once the calibre is completely finished and ready to be cased up.

Recto-verso of the dial showing its translucent quality which adds depth to the dial when cased up.

The gold minutes, hours and seconds hands with the blued steel serpentine shaped date hand.

The dial side of the movement, dial removed showing the calendar and moonphases mechanism. Every element is decoratively finished, spotted, straight or circular grained and angled.

The moonphases disc, the lever to its lower right is the manual corrector linked to the case pusher.

The dial and all discs removed. The yellow wheel assembly at the bottom of the image is the primary drive wheel for the calendar and moonphases system. The levers are a combination of correctors to manually adjust the mechanism, index pawls (or levers) to position the different wheels in a specific position until it is turned, and operating levers which move the different functions automatically by the watch running.

The majority of the components removed from the module.

The levers and springs that contribute to the calendar mechanism.

Month corrector lever

Casing elements. A simple but original and effective corrector system is shown below, avoiding any need for additional pushers or other tools. The individual functions of the module can be adjusted by pushing these correctors with a finger tip towards the centre of the case back.

Case centre with seal in place.

Summary

The overall design and format of the calendar and moonphases is today highly recognisable and used by many different companies, since the 1940’s. The overall technical execution is designed for longevity and will outlive many contemporary versions by other brands. It is solid and simple to assemble and has been well thought through holistically. A significant element although small in appearnace is the under-lug corrector system. Avoiding additional tools reduces the likelihood of damaging the case and keeps the programming process easy.

The exploded module.

Diverse views of the assembled watch.