The Jaeger Lecoultre 880S watch movement, used from 1958 onwards, incorporates several notable features. The winding gear is constructed with beryllium bronze, enhancing its durability. A distinctive characteristic of this movement is the Incastar regulator, which is the first widely produced regulator to include a free oscillating hairspring. The hairspring's end is fixed between two rollers, allowing for length adjustment without isochronism errors caused by the gap between the regulator pins. Additionally, the Jaeger Lecoultre 880S movement is the smallest diameter for a serial automatic movement that includes a sweep second function.