The Cyma Tavannes 426K watch movement, produced from 1955 to 1962, is an open face calibre with a winding gear featuring a rocker on the backside. Its barrel is equipped with a Geneva stopwork mechanism. This movement offers a range of functions, including a timer with options for 1 second, 0.1 seconds, 60 seconds, and 60 minutes, controlled by a pillar wheel. It is also stem windable. The watch incorporates subdials to display 1/10 seconds, seconds, and minutes. Additionally, it includes a stop over wheel on the escape-wheel arbor to measure 1/10-second intervals. It is worth noting that early models may have an additional balance brake.