Up for grabs is a beautifully aged **Seiko SBDC003 Blue Sumo**, a beloved Japanese Domestic Market (JDM) dive watch with genuine tool-watch heritage. This is the first-generation “Blumo” – the original blue-dial Sumo that helped define Seiko’s modern dive line. **Key Specs** \- **Case Diameter:** \~44.7 mm (without crown) – a bold wrist presence without going oversized. \- **Case Thickness:** \~13.3 mm – solid wrist feel with vintage dive vibes. \- **Lug-to-Lug:** \~52.2 mm – wears comfortably across a range of wrist sizes. \- **Lug Width:** 20 mm – easy strap/band options. \- **Water Resistance:** 200m \- **Movement:** Seiko **6R15 automatic** — hand-winding & hacking, \~50 hr power reserve, 23 jewels. \- **Crystal:** Domed Hardlex for rugged durability. \- **Bezel:** 120-click unidirectional dive bezel with lumed pip. Introduced in **2007** as part of Seiko’s first generation of modern “Sumo” divers, the SBDC003 is iconic among enthusiasts for its blend of classic dive tool functionality and standout blue dial — earning it the nickname **“Blumo”** in collector circles. Early Sumo models like this **don’t carry the later Prospex “X” logo**, which many purists appreciate for its clean, original look. **Condition & Extras:** \- Worn and battle tested condition with normal signs of wear \- Strapsco Seiko Sumo bracelet