Cal. 122 is an 18 ligne stopwatch movement produced by Vénus in the 1930s and 1940s. It used a 5-column wheel to control a 1/5 second central stopwatch hand, with a 30 minute counter subdial. One version of the movement features a 30 second dial with 1/10 second accuracy and a 15 minute counter. Additional models had other timer modules.
The stopwatch is controlled using a pusher located at 10:30 on the dial. It is wound using the crown, and lacks timekeeping or any setting mechanism.
Most Cal. 122 movements are found in Léonidas stopwatches and are often stamped with both companies’ hallmarks. Léonidas and Berna versions feature the patented spare parts container embedded in the movement, while those produced for other brands to not.
More detail on the history of Vénus is available in the Grail Watch article, “The Rise of Vénus, Legendary Chronograph Maker“