The Ronda 217P-21 watch movement, produced from 1962 onwards, features an open face calibre design. Its winding gear is equipped with a rocker located on the back side, while the barrel incorporates a Geneva stopwork mechanism. This movement is characterized by several functions, including a timer with a range of 1 second (0.1 second precision), 60 seconds, and 60 minutes. It utilizes a pillar wheel for smooth operation. The watch movement is stem-wound and includes sub-dials for tracking 1/10 seconds, seconds, and minutes. Additionally, it includes a stop over wheel on the escape-wheel arbor for 1/10 seconds measurement. It is worth noting that earlier versions of this movement also feature an additional balance brake.