Seiko Tuna is the name given to Seiko's 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”.
Seiko Tuna SBBN031
The Seiko Tuna collection boasts of many firsts. The collection was the first to feature a titanium/stainless steel shroud, a monocoque case, an L-shaped gasket, and a vented rubber strap. Primarily built for functionality, the Seiko Tuna watches can withstand great depths as tools for professional divers.
Built in 1975, the first Seiko Tuna watch was created in response to a letter the company received in 1968. A saturation diver from Kure City in the Hiroshima, Japan sent a complaint regarding Seiko divers watches, which the company had been making since 1965. These pre-Tuna models were not robust to impact and could not withstand exposure to deep underwater pressure for prolonged periods.
Seiko engineers took on the challenge to create the “ultimate professional diver’s watch. These engineers, led by Ikuo Tokunaga, decided to develop the new Seiko Tuna watches for saturation diving from the start. Tokunaga and his team began development in 1968 and released the first Seiko Tuna watch seven years later with more than 20 patents.
The Marine Master Professional 300M Tuna Ref. SBBN031 is powered by Seiko's iconic high tech quartz movement, 7C46. The 7 jeweled movement with extremely hi-torque tolerances and high efficiency enables the gears and pinions to move and turn the hands in perfect sync to the energy-pulse, with much less kinetic effort via the electronic step motors that power them. Thus making for a highly accurate and efficient full size quartz machine to perform strongly with much less resistance resulting in longer battery life.
Fine satin brushed on shroud
The 47mm stainless steel case might sound intimidating at first glance. But because of the "lug-less" design, the case is only 47mm lugs to lugs. That means this "Tuna" sits so comfortably on the wrist. In fact we think it fits more like a conventional 42mm watch with lugs. The stainless steel case and shroud is fine satin brushed for a up-market feel. We will let the pictures convince you.
Seiko's Lumibrite needs no introduction
The dial's makers and hands are treated with Seiko's Lumibrite for awesome low light visibility. Dual-curved Hardlex for added toughness.
The SBBN031 Tuna comes with a stainless steel bracelet. The satin brushed bracelet with polished details has a ratcheting micro-adjustment for adjustments on-the-go.
Maker: Seiko Japan
Movement: Caliber 7C46. Seiko 7-Jewel Hi-Tech quartz.
Accuracy: +/- 15 seconds per month.
Dial: Matte black with applied luminous indexes
Date: Day/Date 3 O'clock
Case: Stainless Steel.
Crown: Screwdown. Signed Crown
Crystal: Dual curved hardlex
Strap: Stainless steel bracelet.
Water resistance: 300m. ISO certified.
Dimensions: 48mm in diameter, 48mm lug to lug, 14mm thick
Power Reserve: 5 years