Seiko emerged from the Second World War in a state of disarray, and spent the 1950s aggressively modernising its production facilities. As it entered the 1960s, it was poised for a golden decade that would see it move from a position of obscurity to one of dominance in several fields – culminating, infamously, in the introduction of the quartz watch.

In 1960, it introduced the highly engineered Grand Seiko range, and set its sights on the Swiss chronometry trials. It was asked to produce timing equipment for the 1964 Olympic Games in Tokyo (igniting an interest in sports watches), and by 1965, it was said to have the biggest automated production line in the watchmaking world – enabling it to make consistent and accurate watches.

In that very same year, Seiko produced the 150m Diver – its very first diving watch. It may seem laughably insubstantial next to a modern dive watch, but with its squat, rectangular luminous hour markers, rotating bezel and rubber strap, all the basic elements were there. In truth, it was a fair way behind the half-dozen or so Swiss brands that had made great strides since Blancpain introduced the Fifty Fathoms in 1953, but nevertheless it was used to accompany Japan’s 8th Antarctic Research Expedition in 1966.

Seiko
Seiko

Pleased with the response, Seiko pushed on with its work on water resistance and underwater legibility, and in 1967 released the 300m Diver’s. This introduced dotted hour markers and larger hands, doubled the watch’s operating depth and moved the winding crown to 4 o’clock to guard against accidental knocks. In 1968 it was equipped with the 36,000 vph Hi-Beat movement used in the newly-released Grand Seiko timepieces.

The letter that changed everything

But there was a surprise in store. In 1968, as the near-mythical tale goes, Seiko received a letter from a professional diver in Kure City, in the south of Japan. The letter explained that saturation divers working at depths of 350m or more, on the ocean floor, needed watches that were many times tougher than anything Seiko could provide.

Chastened by the letter, Seiko turned inwards, set up a research team, and pledged to create a watch capable of meeting professional divers’ demands.

Just as it had been making ruthless progress at the Swiss chronometry trials (going from finishing 144th to first overall in the space of 5 years), Seiko began a similar period of dogmatic self-improvement for its diving watches. It would not release another new diving watch for seven years.

Seiko Dive Watch Timeline
Scott Bentley/Seiko

The result, when it came out in 1975, was the Seiko Professional Diver’s 600m. Mindful not only of the shortcomings that had been exposed in its previous models, but also of the developments that had gone on elsewhere in the world while it worked towards this singular goal, Seiko’s development team made the utmost efforts to “future-proof” the watch: it was, after all, meant to represent seven years of work. They succeeded.

The main issue affecting deep-sea divers’ watches at the time was helium saturation (divers breathe a mixture of oxygen and helium in underwater workstations to acclimatise to working at high pressure).

Smaller than oxygen, helium molecules were able to penetrate diving watch cases: when the divers ascended, the change in pressure could cause watch faces to crack, pop out or explode.

Doxa (followed closely by Rolex) had developed the helium release valve, a system which is adopted industry-wide to this day. But Seiko went for a completely different approach: a double-layer titanium watch case, impermeable to helium. It was the first diving watch with a titanium case (and, as an interesting side-note, pre-dates the 1980 claims of IWC/Porsche Design to being the first watch ever to be cased in titanium).

It was also antimagnetic, corrosion-resistant and shock-resistant. It retained the Hi-Beat movement, and came on a rubber strap designed to shrink to fit a divers wetsuit under pressure – another common trope among modern dive watches, but a Seiko first.

The Professional 600m answered Seiko’s critics and then some, inspiring Seiko to further “firsts” and cementing its place as a manufacturer of proper diving watches. Not insignificantly, it was also the first Seiko diving watch to pick up a nickname among fans [see below] – a true sign of a cult collectable.

Seiko
Seiko

And now there are two new Seiko divers for fans to name. To commemorate its entry into the world of diving watches, and a half-century of innovation, Seiko has released a pair of Marinemasters, one limited and one not.

It is telling, however, that neither of them really bears the slightest resemblance to the 1965 original. The Marinemaster Professional 1000m Diver’s (which you see at the top of the page) is a throwback to the Professional 600m from 1975.

And the Marinemaster Professional 1000m Hi-Beat 36000 limited edition (above, of which 700 will be produced) is designed to hark back to the second divers watch Seiko ever made – the first with a Hi-Beat movement – in 1968.

You get the impression that the 40th anniversary of the brand getting it right is probably more important than the half-century of the first effort; and perhaps it is, given the relative impact of the two pieces.

Both watches are rated to 1,000m, but have been tested down to 3,000m, affixed to a remotely-operated submersible. Both boast newly-tweaked movements, with improved torque to ensure smooth rotation of the large, luminous hands. Luminosity itself is up 60 per cent on previous models, and Seiko also says their shock-resistance has improved.

The limited edition is the more obviously “new retro” of the two pieces, although with its helium-proof titanium case and patented gaskets there’s no indication it’s intended to spend long in its special presentation box.

The Pro Diver’s 1000m now uses ceramic instead of titanium on its monobloc outer shell (as it has for a few years) and gains an anniversary-appropriate rose gold coating on its bezel and crown.

I’ve no doubt they will both gain nicknames in time – they’re worthy additions to the Seiko canon. But while Seiko is aware of the fandom, you don’t get the impression that it is in any way playing up to it (especially as 48mm watches are not particularly on-trend).

And that’s crucial: the minute these watches become collectibles first and tool watches second, the game is up.