"...Hence, to mark the 50th anniversary of its first automatic chronograph, as well as the 55th anniversary of its first chronograph, Seiko has unveiled a pair of limited editions, both chronographs, naturally. The two editions are each limited to 1000 pieces and powered by the same calibre, the in-house cal. 8R48 that was introduced in 2014."

https://watchesbysjx.com/2019/10/seiko- ... graph.html