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Seiko 55th Anniversary Diver’s Watches – SLA037, SLA039 and SLA041

The Seiko 55th Anniversary Diver’s Watches celebrate the release of the brand’s inaugural diver’s watch back in 1965. The three re-creations: SLA037, SLA039 and SLA041, feature many period-inspired details but encompass sublime blue dials. Mark McArthur-Christie, a self-confessed Seiko fan, provides a fascinating insight into the firm’s prowess for making watches, perfectly suited for life both underwater and on terra firma.

It can feel a little odd at times, this watch business. Here we all are, collecting, talking about, loving even, watches of all sorts. And almost every one of them is, in the real world, as redundant as a lamplighter. Yet it wasn’t always so. One place where watches mattered, to the point of life or death, was underwater.

Diving watches had a simple job; timing how long you were submerged to make sure you didn’t run out of air. That led to a neat trilogy of characteristics; a diving watch had to be legible, even in the dark, robust and waterproof. These are all handy things even when you haven’t got a tank of nitrox on your back. It’s no wonder they caught on.

Although the first diving computers – machines like the analogue Decomputer Mark I in 1955 – were more expensive, less reliable and harder to use than a mechanical diving watch, it was clear that, sooner or later, they’d be taking over.  By the late 1980s, twisting a bezel to time your dive was starting to look as archaic as putting an apostrophe in front of “‘bus”.

Although they came to diving watches later than Rolex, Blancpain and Omega, Seiko did what they do so well; democratised and changed the market in a couple of years starting with their first specialised watch for diving in 1965.  This year, Seiko is celebrating the 55th anniversary of this timepiece, releasing re-creations of three watches that changed the way underwater timing worked; the 1965 Diver’s Re-creation, the 1968 Professional Diver’s 300m Re-creation and the 1975 Professional Diver’s 600m Re-creation. If you’re a Seiko numbering fan, they’re SLA037, SLA039 and SLA041 respectively.

Seiko 55th Anniversary Diver’s Watches

It all started in the early 1960s.  Seiko had been quietly developing prototype diving watches and, in 1965, made its (and Japan’s) first diving watch, the ref. 6217-8000 or ‘62MAS’.  It used a 17 jewel 6217A automatic movement running at 18,000 vph (2.5Hz). The same movement featured in the brand’s 6217 World Time models too.  The stainless steel case was water-resistant to 150m. The dial was clear enough to see from space, with luminous, slabbed five-minute markers and broad, squared off, stick hands. It was the diving equivalent of a spade – designed to do a job, not look pretty. Yet, perhaps because of its focus on function, the watch is a handsome thing.

The 1965 Diver’s Re-creation – SLA037

It’s rugged credentials saw the 62MAS drafted in as timekeeper from 1966 to 1969 on four missions with the Antarctic Team of the Geospatial Information Authority of Japan. At the other extreme, it was also taken up Everest as an expedition timer.

 

Seiko 55th Anniversary Diver’s Watches

The 2020 anniversary limited edition of the 62MAS is remarkably faithful to the ultra-robust original – Seiko has even echoed the texture of the original watch’s rubber strap, although in more modern silicone.  There are other differences under the skin. The anniversary watch – The 1965 Diver’s Re-creation – runs a rather more sophisticated high-beat, 36,000 vph (5Hz) 8L55 movement with a 55-hour power reserve and 37 jewels. Water-resistance is up by 50m to 200m as well. The Re-creation uses a larger, screw-down crown, typical of the later 62MAS watches.

The original lume is replaced with the significantly brighter LumiBrite. Give it enough light (500 lux – that’s about as bright as your office, assuming you still go to one) for about 10 minutes and your watch will glow happily for five hours.

The Re-creation is antimagnetic too, and OK up to 4,800 A/m, which sits it happily in the criteria for meeting the international standard ISO 764 Horology—Magnetic resistant watches as well as DIN 8309.

The 1968 professional diver’s 300m Re-creation – SLA039

By 1968, diving technology had moved on and professional divers were looking for even more robust watches that could safely go deeper.  Seiko had already looked at case technology, realising the way to improve water resistance was to remove seams, joints and access points rather than simply reinforcing them.  They developed the 6159, with double the MAS’ resistance rating at 300m, thanks to a crown that screwed in as well as a new design of monobloc case.

The 6159 also held the hi-beat 25 jewel 6159A (and later B) movement, more often found in Grand Seiko models.

Seiko 55th Anniversary Diver’s Watches

Seiko has taken the 6159 and updated it for 2020, and, like the 1965 Re-creation, fitted it with an 8L55 engine.

The case material for both watches is really rather different though. This is a seriously corrosion-resistant stainless steel that looks at chloride-rich environments like seawater and sniggers quietly to itself.  To give it some context, most decent stainless steel watches will use 316L steel.  This has a PRE-value (pitting resistance value) of 25, give or take. To put that in context, when was the last time you saw a rusty stainless steel watch that hadn’t been dropped off the side of a boat and left on the seabed for a few years? Yet Seiko’s new steel comes in with a PRE-value of around 40. That’s the sort of stuff you’d use for high-grade undersea applications. Seiko, clearly channelling Ronseal (‘does what it says on the tin’) calling it ‘Ever-Brilliant Steel’.  Always good to be seriously over-engineered.

The 1968 Re-creation is a decent 44mm (although, because of the sheer case sides, it seems to wear smaller) and is chunky at nearly 18mm thick. Like its ‘65 sibling, it comes on a modern copy of the original strap.

Conventional diving is one thing.  Saturation diving – where divers are living and working underwater, usually breathing a helium/oxygen mix – is a whole other.  The story goes that Seiko’s management received a letter in 1968 from a professional saturation diver (although to be fair, there aren’t many amateurs) living in Kure, Hiroshima. He complained that his Seiko diving watches kept popping their crystals.  He wrote that he wanted a Seiko that could survive saturation diving with its pressure changes, harsh environment, knocks and, crucially, helium-rich, watch-glass breaking atmosphere.

The 1975 professional driver’s 600m Re-creation – SLA041

Seiko takes challenges like that very seriously indeed. Designer Ikuo Tokunaga started a project to build a diving watch that would do the job. It took him seven years, but he and his team emerged into the daylight in 1975 with the 6159-7010. This used the same hi-beat, GS movement as the 1965 model, the 6159. But that’s where the similarities stopped.

Seiko 55th Anniversary Diver’s Watches

It’s probably fair to say that Tokunaga’s watch was really not designed for looks. Instead, it was intended to do one, highly specialist job; to spend most of its life underwater or in a diving chamber. Yet again, though, its absolute focus on a single function makes it a watch one keeps coming back to.

A 50+mm puck of a watch, the exterior design features alone accounted for more than twenty patents.

Most watchmakers worked on the basis that the tiny molecules of helium that found their way into a watch case when saturation diving need to escape. That’s why professional diving watches often have either manual or automatic helium escape valves.  Ikuo Tokunaga took a typically Seiko approach and thought it made more sense to keep them out in the first place.

To do it, his design brought together an L-shaped gasket to hold the crystal, made from Improved-IIR (Isobutylene-isoprene rubber) and a one-piece titanium case with a ceramic-coated titanium shroud. Titanium made sense as it’s around 40% lighter than stainless steel as well as being exceptionally corrosion-resistant.

This gave the new watch a depth rating of 600m, although it’s been tested to more than 1,000m without any ill effects. In 1983, a later quartz variant of the 600m found itself strapped to the exterior of the research submarine “SHINKAI 2000” and dropped to 1,062m. The remarkable case kept everything ticking happily.

And, in the early 1980s, the Japan Agency for Marine-Earth Science and Technology tested a range of diving watches under saturation diving conditions. Seiko’s Diver’s Professional 600M demonstrated it was ten times more impermeable to Helium gas than its test-mates.

With looks that would scare an angler fish, the watch was bound to end up with a nickname. For a while, ‘hockey puck’ seemed to be the name of choice but, finally, its appearance and capability gave the wags what they needed; ‘Tuna can’ stuck. Despite the nickname, the recessed lugs on the Tuna mean it’s perfectly wearable, even if it won’t easily go under a shirt cuff.  After all, it was designed to go over the cuff of a diving suit.

The 2020 re-issues haven’t left the Tuna out.  The 1975 Professional Diver’s Re-creation carries the Caliber 8L35.  Like the ‘65 and ‘68, the movement was both developed and assembled in Seiko’s Shizuku-ishi Watch Studio. The 8L35 is a 26 jewel, automatic movement with 50 hours of power reserve and a 28,800vph (4Hz) balance.

As a full-on pro diver, the 1975 Re-creation has an anti-magnetic resistance of 40,000 a/m thanks to its pure iron dial. It’s rated at 400m more than its grandfather with a 1,000m water resistance tag. And, this time, the bezel is made from Seiko’s Ever-Brilliant Steel.

The strap on 1975 Re-issue is, again, a modern silicone copy of the original rubber wave strap. The strap’s waves are designed so that you can strap the watch tightly to your diving suit and, as your suit contracts under depth pressure, your watch will stay securely on your wrist.

With their 1990 Scuba Master – the world’s first computerised diving watch – Seiko themselves helped the mechanical divers they’d championed into retirement. The nearest you’ll get now is wearing one as a backup. But that in no way detracts from their interest, their history or, indeed, their very practical, everyday use.  You’d know that almost no matter what you did with it, your watch would be just fine.

 

Seiko 55th Anniversary Diver’s Watches – the 1965 Diver’s Re-creation

Seiko 55th Anniversary Diver’s Watches

  • SLA037
  • Caliber 8L55
  • Driving system: Automatic
  • Vibrations: 36,000 vibrations per hour (10 beats per second)
  • Power reserve: 55 hours
  • Number of jewels: 37

Specifications

  • Ever-Brilliant Steel case
  • Box shape sapphire crystal with anti-reflective coating on the inner surface
  • Screw-down crown, screw case back
  • LumiBrite on hands and indexes
  • Water resistance: 200m diver’s
  • Magnetic resistance: 4,800 A/m
  • Diameter 39.9mm, Thickness: 14.7mm
  • Silicone strap
  • Approximate recommended retail price in Europe: €6,500 (as at 5.3.2020)
  • Limited Edition of 1,100

 

 

Seiko 55th Anniversary Diver’s Watches – the 1968 professional diver’s 300m Re-creation

Seiko 55th Anniversary Diver’s Watches

  • SLA039
  • Caliber 8L55
  • Driving system: Automatic
  • Vibrations: 36,000 vibrations per hour (10 beats per second)
  • Power reserve: 55 hours
  • Number of jewels: 37

Specifications

  • Ever-Brilliant Steel case
  • Dual-curved sapphire crystal with anti-reflective coating on the inner surface
  • LumiBrite on hands and indexes
  • Water resistance: 300m saturation
  • Magnetic resistance: 4,800 A/m
  • Diameter: 44.8mm, Thickness: 15.7mm
  • Silicone strap
  • Approximate recommended retail price in Europe: €7,000 (as at 5.3.2020)
  • Limited edition of 1,100

 

 

Seiko 55th Anniversary Diver’s Watches – the 1975 professional driver’s 600m Re-creation

Seiko 55th Anniversary Diver’s Watches

  • SLA041
  • Caliber 8L35
  • Driving system: Automatic
  • Vibrations: 28,800 vibrations per hour (8 beats per second)
  • Power reserve: 50 hours
  • Number of jewels: 26

Specifications

  • Titanium inner case (super hard coating) with Ever-Brilliant Steel bezel
  • Sapphire crystal
  • LumiBrite on hands and indexes
  • Water resistance: 1000m saturation diver’s
  • Magnetic resistance: 40,000 A/m
  • Diameter 52.4mm, Thickness: 17.2mm
  • Silicone strap
  • Approximate recommended retail price in Europe: €4,500
  • Limited edition of 1,100

 

 

Further reading

https://www.seikowatches.com/

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