A closer look at the Seiko 55th Anniversary Trilogy of diver's watches

They may have launched their first diver’s watch only in 1965 – more than a decade after Swiss brands like Rolex – but over the next 55 years, Seiko has built an enduring legacy for itself. The brand’s durable and purpose-built divers have spawned a cult following among watch aficionados today. Seiko’s first diver’s watch in 1965, the Ref. 6217-8000/1 or 62MAS (the name is derived from autoMAtic Self-dater), was also the first one made in Japan. Water-resistant up to 150 meters, members of the Japanese Antarctic Research Expedition from 1966 to 1969 were famously supplied with this watch on their mission.

Three years later, Seiko introduced the Ref. 6159-7000. Not only was this watch depth-rated to 300 meters thanks to its distinct monobloc case and screw-down protection crown, it was the first time a diver’s watch was fitted with a high-beat mechanical movement (the balance wheel oscillated at 5 Hz or 36,000 vibrations per hour). In the 1960’s this was like dropping an air-cooled Porsche engine into a Land Rover Defender. In the same year, Seiko received a letter from a commercial diver who requested a solution to a problem he was having - his dive watches were no good in actual work situations, sometimes at 600 meters below sea-level. Professional divers breathe helium mixed with oxygen at extreme depths and helium tends to seep into the case through the watch’s rubber seals. When divers go through the required decompression on their way up in diving bells, helium is released through special escape valves in diver’s watches (as seen in the Rolex Sea-Dweller or the Doxa Sub 300T). Without a helium release valve, the watch crystal would crack as a result of the pressure.

The letter galvanised Seiko’s product development team into action. It took seven years to find a solution, but their riposte to that fateful letter is today considered one of the greatest purpose-built diving watches ever. Under the guidance of engineer Ikuo Tokunaga, Seiko developed the Ref. 6159-7010 - it was the first diver’s watch to use a titanium case, the case had a distinctive ceramic-coated titanium protective shroud. The movement was top-loaded into the monobloc case and an L-shaped gasket was used to hermitically seal the watch, the first of its kind in the industry. This provided a better protection than a deforming round gasket and allowed Seiko to forego the use of a helium-release valve even though the watch was depth-rated to 600 meters. It looked like hockey puck or a can of tuna. Initially nicknamed “Tuna” by collectors, it is now referred to as “Grandfather Tuna” among the Seiko faithful.

These three watches laid the foundation for a series of professional-spec watches that would eventually evolve into what is now known as the Prospex series. Even Roger Moore’s James Bond wore Seiko diver’s – Ref. 7549-7009 ‘Golden Tuna’ 600m Professional Quartz in 1981’s For your Eyes Only and the Ref. H558-5000 with a digital-analogue display in 1985’s A View to a Kill.

The 55th Anniversary Editions

To mark the 55th anniversary of the 62MAS, Seiko produced a trilogy of vintage re-issues this year. The three watches were based on the 62MAS, the hi-beat Ref. 6159-7000 from 1968, and the Ref. 6159-7010 “Grandfather Tuna”. All three watches use a case made from a brand new proprietary steel alloy called “Ever-Brilliant Steel”, it is supposed to be more corrosive resistant than the 316L variety commonly used in the industry.

To support this claim, Seiko has cited the “extensive” use of the material “in the surfaces, linings, bolts and other components of marine structures and vessels so as to avoid corrosion in a chloride-rich environment such as sea water.” The PREN (Pitting Resistance Equivalent Number) value of the alloy is 1.7 times higher than 316L steel. It is also brighter than traditional steel and that’s down its natural colour and not sleight of polishing.

REF. SLA037: This is actually an evolution of the Ref. SLA017 launched in 2017 which was based on the 62MAS from 1965. It has a 39.9-mm brushed Ever-Brilliant Steel case with a large screw-down crown and a black 60-minute unidirectional diving bezel. The case is depth-rated to 200 meters and features a solid caseback. The blue-grey dial of the watch is protected by a vintage-style “box-shaped” sapphire crystal meant to recall the acrylic used in such models historically. Inside is the Hi-Beat 8L55 automatic caliber with a 55-hour power reserve. Limited to 1,100 editions, it will retail at AED23,950.

REF: SLA039: Based on the Ref. SLA025 — the GPHG-award-winner from 2018 — which was a re-issue of Seiko’s first Hi-Beat diver, the Ref. 6519-7000, this timepiece has a monocoque Ever-Brilliant Steel case. It has a screw-down crown and a black unidirectional 60-minute diving bezel. The beating heart of this watch is the same 8L55 self-winding movement as in the previous model. Limited to 1,100 pieces, it will sell for AED17,00.

REF: SLA041: The final model of the trilogy is a hat-tip to the “Grandfather Tuna” Ref. 6159-7010 from 1975. The reissue opts for a traditional titanium case and only uses “Ever-Brilliant Steel” on the bezel. It maintains a whopping size on the wrist, it is 52.4-mm-wide and 17.2-mm-thick.

It has a screw-down crown, a thick, toothed unidirectional 60-minute bezel in black with white accents, and a black protective outer shell with a “super hard” coating. The case is depth-rated to 1,000 meters. It is powered by the automatic caliber 8L35, which beats at 28,800 vph and stores a 50-hour power reserve. Limited to 1,100 editions, it will sell for somewhat less, at AED17,000.