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.

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 the “lug-less” design means this “Tuna” sits so comfortably on the wrist. So 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.

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.