The Seiko 5 Sports SRPD51 is the blue model of the 5 Sports SKX series, the 2019 collection that collectors nicknamed the “5KX” because it took over the design of the discontinued Seiko SKX diver. Its stainless steel case measures 42.5 mm in diameter, 13.4 mm thick and 46 mm from lug to lug, with a 22 mm lug width. The blue sunburst dial is matched by a blue unidirectional rotating bezel, and the hands and indexes are coated with Seiko’s LumiBrite. The dial sits under a Hardlex crystal. Inside is Seiko’s caliber 4R36, a 24-jewel automatic movement that can also be wound by hand and has a hacking seconds hand, with a power reserve of about 41 hours. Water resistance is 10 bar (100 meters), and magnetic resistance is 4,800 A/m.

The watch shows hours, minutes and seconds with a day and date display at 3 o’clock. The screw-down caseback has an exhibition window that shows the 4R36 movement. It comes on a stainless steel bracelet, 22 mm wide at the lugs, with a three-fold clasp that has a secure lock and push-button release. The complete watch weighs about 170 g. The same SKX-series case is offered in many other dial, bezel and strap combinations. Seiko USA lists the SRPD51 at USD 350.

Reviewers widely describe the SRPD as the natural successor to the SKX007, keeping its proportions and look while adding a movement that hacks and hand-winds and a display caseback. The main criticisms are that it is no longer an ISO-rated diver: water resistance drops from the SKX’s 200 m to 100 m, and the crown is push-pull rather than screw-down. The Hardlex crystal is another reminder of its price. Even so, its value, robust build and huge range of colours have made it one of the most popular entry-level mechanical watches and a favourite base for modders. The SRPD51 is currently in production and sold through Seiko’s official US online store.