https://www.seiko-design.com/140th/en/topic/81.html

Seiko's proprietary Kinetic mechanism generates electricity from the movement of the wearer’s arm, eliminating the need for periodic battery replacement. The Arctura was born in 1997 as a global strategic model of a watch with this mechanism. The advanced design, created by a well-known German watch designer, combined both aesthetic design and wearability, with a sense of unity from the case to the bracelet and intricate molding around the crown achieved by MIM (metal powder injection molding). As there is no need for periodic battery replacement, the back of the watch is a one-piece construction with no unevenness in the case back. The bracelet, composed of urethane and stainless steel, fits comfortably on the wrist and stands out.