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The Omega Seamaster 600 Plongeur Professionnel Ref: 166.077 Mk 1, AKA "The Ploprof"

The Seamaster Ploprof 600 is the ultimate epitome of the "tool watch". Its very name denotes its raison-d’etre: Plongeur Professionel (Plo-Prof), a translation from French for Professional Diver.

Holding the watch, you can feel its girth and its weight - with a 55mm case diameter it's one of Omega's most recognisable creations. Surprisingly, it actually contours the wrist pretty well, in the main probably down to its shape

The Compagnie Maritime d’Expertise (Comex) was founded in 1961, and pioneered most of the early work in deep sea diving and engineering. The late 1960s and the race for oil saw the growth of deep commercial and "saturation" diving, and after the success of the Seamaster 300, Omega (on request by Comex) wanted to make an even more reliable and waterproof wristwatch.

Being at such depths, for a prolonged period of time can cause a build up of helium inside the watch case, which could cause the crystal to blow off during decompression if the diver forgot to unscrew the crown.

While watch manufacturers like Rolex and Doxa worked incrementally to develop the helium escape valve (HEV) found on many of today’s dive watches, Omega went down a completely different route and aimed to eliminate the helium issue by preventing any getting into the watch in the first place.

The Seamaster 600 (waterproof to 600m) first saw the light of day in 1970/71, more than 4 years after production was started. The watch itself had been in development for 9 years and at the time of release it cost so much (more than twice the price of a Rolex Submariner) only top professional divers went for the Ploprof.

Hugely over-engineered, the Ploprof 600 was revolutionary in many aspects. The case was machined from a single block of stainless steel and this tank-like structure prevented the case from flexing under pressure.

Since it was a monobloc design, water could only enter the watch from two points: the crystal and the crown. The 4mm thick crystal was screwed down onto a gasket by a steel ring, resisting both internal and external pressure. The crown was also designed in a unique way, acting as a nut that pulls and seals the crown.

The bezel locking system was also a first, using a pushbutton to unlock the bezel mechanism only for setting purposes. The dial either in navy blue or black to ensure it was readable under any condition, with a massive, striking minute hand.

This watch has a "B1 bezel", which is recognisable by its no serif, flat-top font - God, we love the fonts of this era.

For its mechanism, the Mk 1 Ploprof uses the workhorse Cal.1002, a caliber with 20 jewels and date that beats at 28,800A/h and has a power reserve of 42h (even now!).

This watch remains one of the most effortlessly wacky and classy tool watches out there. The Omega Seamaster Ploprof is a true icon, recognisable by those with even a passing interest in watches. Just ask Agnelli, the billionaire ex-head of Fiat and Ferrari.

To get your hands on a prime example of such a watch, have a look at ours, for sale, here:

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