The 4400 family used a slower 18,000 A/h oscillation rate than the derived Hi-Beat Calibre 4500, which replaced it in 1968. But it was accurate enough for use in high-end Seiko watches and allowed Daini to challenge Suwa Seikosha in the production of Grand Seiko watches. One unique aspect of this movement in the King Seiko 44KS is that a tiny weight was attached directly to the hairspring to improve accuracy. This is often removed during servicing, since most watchmakers are unfamiliar with this practice.
The 4400 was best known as the movement used in the legendary Grand Seiko 44GS. Introduced in 1967, the 44GS set the styling trend for all future Seiko watches and has been revered ever since. Seiko even created a replica 44GS in 2013, powering it with a special hand-wound 9S64 movement to duplicate the 4420 as closely as possible.