

1972-seiko-catalog-s1-jp, page 2
Often called the "final King Seiko," Daini's last mechanical KS series and its most advanced automatic, with caliber 5246 featuring instantaneous day/date change at midnight (versus the slower rolling change of the 56 series). Crucially, the 52-series is the direct ancestor of the modern 9S movement family in today's Grand Seiko. Daini pieces wore "Special" dial branding; scarcer than the 56KS.