The Seiko Prospex SPB531 merges heritage watchmaking with outdoor spirit. Drawing inspiration from mountain-night skies, it features a vertically brushed deep-blue dial, cathedral-style hands, and a gold-tone seconds hand for a refined touch. Housed in a 39.5 mm stainless steel case (13.2 mm thick) with screw-down crown and exhibition case-back, it introduces an internal rotating compass bezel for orientation.