The Citizen 1131 is a mechanical watch movement introduced in 1968. It incorporates combined settings for the escape wheel and third wheel, known as Diafix. Unlike traditional manual-wind calibers, the winding gear is integrated within the movement. This unique design, along with the indirectly driven minute hand, contributes to a robust movement with a comparatively large balance and slim profile. The Citizen 1131 offers various functions, including automatic winding, a sweep second hand, a quickset date feature, dual time capability with a 12-hour display, and a hack feature. It has been utilized in watches since 1968.