The Ronda 015P-21 watch movement is an open face calibre that was used during the period of 1955-1962. Its winding gear features a rocker on the backside, while its barrel is equipped with a Geneva stopwork. This movement incorporates several functions, including a timer with pillar wheel control for 1s (0.1s), 60s, and 60min measurements. It is also stem-wind and includes sub-dials for 1/10 seconds, seconds, and minutes. Additionally, this movement features a stop over wheel on the escape-wheel arbor for precise 1/10-second timing.