If Seiko’s early “Tuna” references seem over the top, well, that’s because they are. More than just a dive watch, the first “Tuna” model was a response to harsh, albeit deserved, criticism. After the success of the 150m 62MAS in 1965, Seiko doubled down and set out to engineer their first true professional diver. The resulting 6215, and hi-beat 6159 models were built to withstand conditions at 300m. Both were large, imposing designs with solid monocoque cases that performed well in controlled environments. However, in 1968, a saturation diver from Hiroshima penned a letter to Seiko informing engineers of critical shortcomings in construction experienced during real world applications. Rather than admit defeat and bow out, engineers at Seiko saw an opportunity to rise to the occasion and not only meet these challenges head on, but to exceed all expectations. They spent the next seven years developing the perfect professional diver’s watch. In that time, more than 20 patents were applied for and granted during the process. The result was unveiled in 1975, and what we now refer to as the “Grandfather Tuna,” was a checklist of diver’s watch innovation. With a rating of 600m, it’s features are too many to list here, and it surpassed every ISO testing standard available. Just three years later with the advent of quartz technology, Seiko went back to the well and delivered its first quartz driven “Tuna” diver. It shares many characteristics with its predecessor, however, to further improve durability, its titanium case was plated in a super ceramic titanium nitride that spurned yet another nickname: the “Golden Tuna.” So named for their resemblance to tuna’s classic packaging, these shrouded divers are still very much a part of seiko diver identity. Early variants are list toppers for collectors, and the build quality alone means that many not only survived, but have remained in great cosmetic condition even decades later. This example from January of 1981 is unpolished, and completely original aside from a replacement mineral crystal. The textured matte black dial is virtually flawless, and the original luminous material is clean throughout. The colossal hour and minute hands sport a horizontal machined finish that creates an iridescent light show from every angle, and a cross support helps to ensure stability of the large luminous windows. The second hand is a black and white reverse “lollipop” that meets the chapter ring hash marks at every tick. At a massive 4mm thick, the crystal is beveled, stepped, and secured by a screw down ring and gasket assembly to ensure resistance to water under pressure. The bezel is a classic “count up” layout with a relief insert beneath an acrylic overlay. The large knurling along the bezel’s edge makes for easy rotation, and a dual ball bearing assembly provides smooth action and stability at every click. The PVD shroud bears some light wear, but the plating is completely intact, and it’s mounted with the original screws. At 8mm, the grooved crown is easy to manipulate, and screws down securely with ample threading. The case back markings are crisp and complete with the “Tsunami” engraving at center. It comes attached to an Uncle Seiko “GL-831” flat vent composite for a fit and finish as close to the original as it gets. The buckle is the genuine Seiko titanium nitride and steel tang from the from the original strap. Post service and with a fresh battery installed, the 7549 driving the hands is keeping perfect time. Robust, rugged, and reliable, it’s ready to be the toughest “tool” in the box.

Uncle Seiko Black “GL-831” Flat Vent Composite / Original Seiko Titanium Nitride Tang Buckle

Serviced- 6/25

Diameter- 49mm

Lugs- 22mm