/ / / Seiko Prospex Marinemaster Tuna NWW 1823

Seiko Seiko Prospex Marinemaster Tuna NWW 1823

Seiko Prospex Marinemaster “Tuna”

Unused looking condition Seiko Marinemaster nicknamed Tuna reference SBBN031. It is a collectible model as it is now discontinued and sold out. Comes complete with box and papers, warranty dated July 2020. This is a Japan only market model so difficult to get elsewhere in the world. Seiko Tuna is the name given to Seikos range of watches designed for scuba and professional diving. In particular. Seiko made these watches with saturation diving or greater depth diving in mind. All of the watches in the Seiko Tuna range are characterized by protective screwed on shrouds that have earned them the nickname of Tuna. This in addition to the special gaskets could not allow helium to enter the watch and therefore no need for a helium escape valve for saturation diving. This presented a unique and robust professional divers watch.



  • Stainless steel case
  • One-piece Construction
  • Steel bracelet wit push button release and fliplock saftey
  • Sapphire Crystal
  • 7C46 Quartz Caliber
  • Screw Down Crown
  • ~5 Year Battery Life
  • Accuracy of +/-15 Seconds per Month
  • Water Resistant to 100 Bar / 1000m
  • Designed for Saturation Diving
  • LumiBrite Paint on Hands and Markers (Retains Light for 3 to 5 Hours)
  • Second-hand Stop Function
  • Resistant to Magnetic Interference
  • Day/Date Display
  • 48mm Case Diameter
  • 4mm Case Thickness
  • 22mm Band Width
  • Weight 114g

Key Characteristics

Brand: Seiko
Band: Steel Bracelet
Case Material: Steel
Condition: Mint
Movement: Quartz