If the 1950s saw the rise of recreational diving, with the birth of the Rolex Submariner and the fake Omega Seamaster, then the late 1960s and the “race for oil” saw the growth of deep commercial and “saturation” diving. This highly specialised technique involved divers living in pressurised environments for prolonged periods of time, breathing a mixture of helium and oxygen, only decompressing at the end of the tour of duty. Rolex became aware of a problem of helium build-up inside the watch case, which could cause the crystal to blow off during decompression if the diver forgot to unscrew the crown. This lead Rolex and Doxa to develop the helium escape valve (HEV) found on many of today’s dive watches.
Omega, working with the leading technical dive company Comex, followed a different route. If Rolex evolved incrementally, building on what they already had, Omega was revolutionary, creating something completely new. The best 1:1 replica Omega Seamaster 600 Plongeur Professionnel (Ploprof) aimed to eliminate the helium issue by preventing any getting into the watch in the first place.
Hugely over-engineered, the tank-like watch case would not flex under pressure. Milled from a single piece of steel, with the movement loaded from the front, the only seals were around the crystal and crown. The 4mm thick crystal was screwed down onto a gasket by a steel ring, resisting both internal and external pressure. What appears to be the crown is actually a large nut that drives the square-topped crown in and out on a screw thread. This prevented torsion to the crown gaskets, prolonging their life, but the huge crown guards necessitated placing the crown on the left of the watch to allow the wearer’s wrist to flex. Tests showed that the black bezel Omega fake dive watch could survive simulated depths of 1,370 meters and only stopped working when the crystal was pressed down to touch the seconds hand. The distinctive “big red button” unlocks the bezel, allowing it to turn in either direction, a function more important for shallower diving because saturation divers could remain at work for hours on end.
The Seamaster 600 Ploprof is indicative of Omega’s design creativity. Sadly, its fruitful relationship with Comex was terminated just as the Ploprof was launched to the public in February 1971; Comex instead made a deal with Rolex, which offered to gift 100 Comex-branded Sea-Dwellers to the company each year for test purposes.
Buying a vintage Ploprof is a good bet if everything is correct, and with auction prices hovering around £4,000 they are reasonably affordable for an historically interesting dive watch. Remember, though, these were tools that needed to be maintained, so service parts and movement replacements are common, making an archive extract from Omega a wise addition to any purchase.
If you want a modern option, however, Omega does have up-to-date versions in its collection. The Swiss movement copy Omega Seamaster Ploprof 1200m starts at £9,730 and is powered by a magnetic-resistant calibre 8912, visible through the case back.