The Rolex 3055 watch movement, utilized by Mido between 1935 and 1954, incorporates a base plate derived from the AS 1131/1132 movement. It offers the choice of black rhodium plating or pink-gold plated train. Additionally, it features the Incastar regulator, which stands out as the sole extensively manufactured regulator to employ a freely oscillating hairspring. The regulator's design secures the end of the spring between two rollers, actively adjusting its length and thereby eliminating any isochronism error stemming from a gap between the regulator pins. The Rolex 3055 movement includes automatic (bumper) functionality and a sub-second feature.