The Sumo which was first released in 2007 for the Japan Domestic Market JDM, came in three variants – SBDC003 (blue dial with metal bracelet), SBDC001 (black dial and metal bracelet) and the SBDC005 (orange dial with rubber strap). Sturdily built with an aluminum bezel, the watch runs the Caliber 6R15 movement and has a 50-hour power reserve thanks to the use of Seiko’s proprietary Spron alloy mainspring and is rated anti-magnetic. In 2019 Seiko came out with upgrade versions for both the International Market and JDM where the crystal material is finally changed from hardlex to sapphire crystal and the movement from 6R15 to 6R35 increasing the power reserve to 70 hours.
