Longines Automatic, Cal.: 22AS Prototype, 1946
Category: functional prototype
Description: Stainless steel cased prototype. Snap case back, outside unmarked, inside with firm and info. Silvered copper dial with Arabic numerals (pair) and hour dots (unpair). Black printed minute track with Arabic five minutes indexes. Printed ‘Longines Automatic’ at ’12’, mostly cut by big circular hole revealing the main spring. Hour numerals and dots highlighted with radium. Blued steel hands, hour and minute hands highlighted with radium.
Dimensions: 33.8mm, lug – lug: 45.8mm, lug width: 17.8mm
Movement: Longines calibre 22AS prototype, unnumbered, unmarked
Additional Info: In 1945, Longines managed to introduce a new approach to the ‘automatic’ self winding system by inventing an eccentrically wound method, using a 360° rotor and allowing for bi-directional winding. This caliber 22A featuring sub-seconds at ‘6’, was a revolutionary caliber, because for the first time the efficiency of the self winding system was increased not only because of the 360° turning rotor, wich Rolex used already since 1931, but primarily due to the bi-directional winding. It is thought that not more than 6 prototypes were made for the primary development of this system (cal.: 22A) with sub-seconds at ‘6’.
During the late 1940s and specifically after WWII, time-only watches with sub-seconds started to become out of fashion, manufacturers concentrated in developing calibers with central seconds judged aesthetically more harmonious and breaking completely with the outdated pre-WWII style. The adaptation of Longines’ new self winding system (cal.: 22A) for center seconds presented several major obstacles. The most important obstacle being the wheel transmitting the movement onto the centrally located seconds wheel, which traditionally would be mounted on top of the wheel bridge and thus blocking the movement of the rotor. by optimising the inter-bridge distance, the engineers managed to house the aforementioned transmitting wheel underneath the bridge, clearing the way for the rotating weight.
The watch presented here seems to be a rare survivor of the prototypes made for this center seconds, self winding caliber. The big aperture in the dial and the movement, including the main spring casing was made to allow for the observation of the functionality of the bidirectional winding of the mainspring during functional testing on the wirst. If this movement is one of the 6 caliber 22A prototypes mentioned above, but modified for the center seconds system remains unknown.
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