The Unitas 431 watch movement, introduced in 1932, features a Breguet hairspring and variations in pillar plate sizes amongst its series 281 through 284. This manual-wind chronograph movement includes a 60-second counter, as well as 30-minute or 45-minute counters, all controlled by a pillar wheel mechanism. It also includes a sub-second function and offers additional options such as a 12-hour counter and calendar functions similar to the 281 series.