Stevens had found the perfect match for his deep-diving career. He walked out with an Omega Seamaster 600, known as the Ploprof, and to this day, he says it’s the most expensive thing he’s ever treated himself to on a whim.

A tech diver working in the North Sea was exactly the sort of customer Omega made the Seamaster 600 for. As diving technology rapidly advanced in the wake of the diving boom that began in the late ’50s, timepiece manufacturers raced to introduce new technical innovations that allowed watches to function better at deeper depths. Innovations like the helium escape valve, found on the Rolex Sea-Dweller (the technology may have been developed by Doxa, or Rolex, or co-developed by both), allowed the watch to remain impervious to the detrimental effects of decompression chambers; without it, the crystal was at risk of popping out of the watch.

Then there was the Super Compressor case, manufactured by EPSA, which utilized a design that sealed the watch even tighter as atmospheric pressure increased. The Ploprof didn’t use any of that. Instead of addressing how helium would exit the watch, Omega engineered a case that wouldn’t even let any helium ingress occur in the first place, and in order to achieve maximum water resistance, the case was constructed in a monobloc fashion, meaning it’s one single piece, rather than using multiple components, like a traditional screw-in caseback. The idea behind the monobloc case is that there is one less point where water could enter the case.

When Omega set out to design a dive watch for professionals in the mid-’60s, it didn’t start with an existing design and iterate. The iconic Seamaster 300 was in Omega’s catalog at the time. Instead, the company started from the ground up to create two “Ploprof” models. The name is derived from Plongeur Professionnel, meaning “professional diver” in French. The Ploprof family consisted of the Seamaster 600 (ref.166.077) and a prototype of the Seamaster 1000 (ref.166.093). The “Ploprof” name only stuck with the 600, however, and the Seamaster 1000 became known as “The Grand” among Omega collectors. It was produced much later in the ’70s, although the first prototype appeared just prior to the Seamaster 600.

A man by the name of Frederic Robert can be credited for the creation of the Ploprof, among a number of other “Professional” models like the Omega Flightmaster and Seamaster 120 “Big Blue” chronograph. He joined Omega in 1967 as an advisor after successfully growing the company Aquastar, which he founded and owned. A “Marine Unit” was set up at Omega under his stewardship, and by 1968, the framework for the Ploprof as we know it today was established under Robert’s unit.

We’ll be focusing on the Seamaster 600, the watch now known simply as the PloProf, and the modern iteration it has spawned. In the late ’60s, while the world was paying attention to who would pull ahead in the space race, there was quietly an “inner space race” happening. The rapid development in aquatic technology was a function of humankind’s drive to explore the world’s oceans. The Ploprof might be a very small piece of it, but it’s representative of a much larger notion of mankind investing heavily in science and technology to overcome the challenges of nature. The Ploprof was worn by the divers that laid the undersea cables that facilitate our modern internet, and the oil exploration that powers our economy to this day. And when it comes to getting things done deep beneath the sea, timekeeping is a life and death matter.

The watch was designed with the intention of meeting the demands of routine use by professional divers, so marketability and aesthetic appeal took the back seat. The sole focus during the conceptualization phase of the Ploprof line was to create something that consistently performed at depth and could be relied on by divers who were on the cutting edge of technical diving. This required constant performance throughout extreme pressure changes that one might face during time in a decompression chamber, or the increase in atmospheric pressure from the surface to roughly 2000 ft. (600 meters) deep. Additionally, the design would need to mitigate accidental advancement of the bezel, as accurate timing at depth is an absolutely crucial element in the field of technical diving.

By 1967, the first patent was filed by Omega, number CH480680, and it outlined a rather unconventional case design. To those who haven’t developed a very specific appreciation for function-driven design, it might even appear misshapen. The case was fashioned from a single block of steel, and this allowed for superior structural integrity and minimal points for water ingress to occur. (It should be noted that Seiko released the 6215-7000 in 1967, and that watch featured a monobloc case as well.) A cavity for the movement is milled out from the case, and the movement and dial assembly is loaded in before being sealed by the crystal. In doing this, it creates a scenario where the more pressure is applied to the crystal as the watch goes deeper, the tighter the seal becomes as it compresses the gaskets.  As mentioned before, there isn’t a traditional caseback present on the Seamaster 600 Ploprof. Where standard watches might have a screw-down caseback, instead the Omega simply features horizontal ridges, meant to hold the watch in place on the wrist, machined in the circular shape of a caseback.

The Seamaster 1000 prototype employed the same top-loading design, but where the Seamaster 600 differs is the bezel-locking mechanism and crown assembly. It’s the bezel-locking mechanism that gives the Ploprof an unusual shape. The locking mechanism is housed on the right side of the case, and the crown on the left. On most watches, the crown is on the right side of the case, but the Ploprof is designed for right-handed divers to be able to operate the locking mechanism – which typically sees more use than a crown – with one hand, and without taking the watch off. In roles like Stevens’ job as a tech diver, accurately measuring elapsed time is needed to successfully complete tasks within a given timeframe, but also to avoid deadly situations as well. The bezel advancing unintentionally is a problem with most dive watch designs of the period, but Omega had engineered out that design flaw with the Ploprof. If one were to turn the bezel without depressing the red plastic button, the bezel wouldn’t budge. The red plastic button takes a significant amount of force to push down, and that unlocks the bezel to be able to be turned freely in a bi-directional fashion. It’s nearly impossible for the bezel to turn unintentionally, and that’s part of the reason modern collectors – and divers in-period – regard the Ploprof as the ultimate dive watch.

The crown works differently than most dive watches of the era as well. The protruding shape of the case on the left side acts as a crown guard, and the crown seats into the case with a square plate attached to the portion of the crown that’s typically gripped. When the crown is engaged, the case features one contiguous line that doesn’t snag on anything and helps prevent any damage to the crown or stem. The crown locking mechanism, when seated properly, forms a seal that’s impervious to any liquid ingress in a way that was simply more secure than anything else of its time.

Early on, titanium prototypes of the Ploprof were developed by casemaker Schmitz Freres. Less than 10 are thought to exist, however. The standard stainless steel Ploprof case weighs 82.5 grams, and the titanium cases weigh 49.5 grams. A common criticism of the Ploprof is that it’s rather unwieldy and heavy on the wrist. The titanium case would have solved this problem, but it was difficult to produce en masse, and it was costly. At the time, titanium had just made its way into commercial and military aircraft. Titanium was in such short supply that the U.S. government had to set up shell corporations and secretly buy it from Russia to produce the Lockheed SR-71 Blackbird reconnaissance aircraft (which was highly classified as well). But the type of steel that Omega settled on was tech-forward in its own right.

According to production notes from Omega, the type of steel used was dubbed “Uranus steel” by the French manufacturer that supplied the metal. This variety of steel featured the addition of molybdenum to help resist the corrosion caused by acids. Omega settled on this specific alloy after studying the effects of underwater welding in saltwater on stainless steel watches. Today, this specific type of steel is often referred to as “904L stainless steel.” The vessels and tools that COMEX built were often fashioned out of 904 steel – it’s a material that’s been proven to stand up to the sea.

The Ploprof in steel was already as expensive as two Rolex Submariners, and titanium would add to the already-high cost. The watch retailed for CHF 690 on the rubber “isofrane” strap, and CHF 720 on a mesh bracelet. During the lifespan of the watch in retail shops, from 1970-79, it was rather expensive compared to its competition.

But it had proven technical chops to back up the price tag. According to an old Omega service bulletin from 1971, each Seamaster 600 Ploprof was actually tested to 1000m of water resistance, making the 600 moniker seem very conservative compared to the limits the watch had been tested to.

In the late ’60s, as part of the testing phase of the Ploprof, divers Christian Cornillaux, Michel Liogier, and Patrick Cadiou wore the watch during Operation Janus. Oil companies Elf/Erap contracted the team of divers working for COMEX to explore and survey the Ajaccio Gulf off the coast of France for eight days. The watch was worn for four hours a day in the field at 253 meters during the operation as part of the testing and development program. COMEX stands for Compagnie Maritime d’Expertises, and the company is known for its expertise in deep-diving operations. COMEX had also pioneered a number of techniques and systems in hyperbaric testing, a technology where certain pressure levels can be created and manipulated in a Hydrostatic chamber. In 1970, if there was any private organization on the planet who would be able to properly test the Ploprof in the environment it was engineered for, it was COMEX.

Omega sent a number of prototypes to Ocean Systems Inc. in Tarrytown, NY to test, and the diving research company came back with a statement claiming the Ploprof was more watertight than a submarine. It isn’t stated by what parameters that test was measured, but the takeaway was clear: The Ploprof was a capable tool for telling time under the surface of the ocean, whether it be the North Sea or the Ajaccio Gulf.

While the Janus project is well-documented in terms of testing the Seamaster 600, according to Petros Protopapas, Head of Brand Heritage at Omega, it was the Seamaster 1000 that was initially slated for testing with COMEX’s “Project Hydra I,” in 1968. Project Hydra was designed to test heliox and hydreliox gas mixtures in order to combat the effects of high-pressure nervous syndrome in which divers experience tremors, visual disturbance, nausea, and dizziness. While the Seamaster 1000 did perform nominally during testing, COMEX decided to go with the Seamaster 600 design for further testing, like the Janus Operation trials.

The Ploprof hasn’t been adopted outside the diving community in the same way other iconic dive watches, like the Rolex Submariner, have been. The price tag and highly specialized nature of the watch meant that a relatively small number were produced. Media captured in the ’70s featuring the Ploprof is usually diving-related, like the Ploprof’s appearance in The Undersea World of Jacques Cousteau, a popular TV show that ran from ’68-’75 in which Cousteau’s team traveled the world’s oceans showcasing aquatic life.

But there is one unexpected champion of the Ploprof who had little to do with diving and everything to do with suave style and corporate balance sheets. It was the famous Italian industrial tycoon Gianni Agnelli, nicknamed the “Rake of the Riveria” for his charming ways and handsome aesthetic. Agnelli wore watches on the outside of his shirt cuff and was known for wearing unusual watches, like the Ploprof, which he wore on a black rubber Isofrane strap.

Perhaps the kooky nature of the Ploprof has limited its success on the auction circuit. Its unconventional aesthetic draws a very loyal, but narrow, legion of fans, which means that the pool of potential bidders stays relatively small, even today. It’s not a watch with mainstream appeal, but instead, it’s limited to collectors with a tight focus on tool watches designed for a singular purpose. Of course, there are plenty of collectors who simply appreciate something drastically different from everything else out there.

Below is a compilation of Ploprof examples sold by Antiquorum, Sotheby’s, Christie’s, and Phillips from 2006 to the present:

In June 2006, a first-generation Ploprof sold by Sotheby’s crossed the block with a realized price of $3,000. A comparable watch, another first-generation model, recently realized $4,000 in September of 2020 by Antiquorum. As a whole, prices for standard production Ploprofs have not varied much over the recent years. But you’ll notice some outliers in the data set, and the highest results, between $33,125 and $90,937, are the prototype watches. Three categories of prototype watches have appeared in auctions: Those produced by Omega that remained unused, potentially for design purposes; then those tested by COMEX divers Christian Cornillaux, Michel Liogier, and Patrick Cadiou in the Gulf of Ajaccio; and finally, watches that were tested by Ocean Systems Inc. of the United States.

The other grouping of high results comes from Omegamania, an auction of important Omega pieces that took place on April 14 – 15 in 2007 at Antiquorum in Geneva. In a story that ran in the New York Times days ahead of the sale, Osvaldo Patrizzi, the chief executive of Antiquorum, said, “This sale should put Omega back in its natural position vis-à-vis other brands. In my view there is no difference from a technology or solidity point of view between Omega and Rolex.” According to the article, the value of Rolex watches rose 30 to 35 percent during the year prior. Patrizzi certainly succeeded in his mission.

Three Ploprof watches were auctioned in Omegamania, none of them prototypes, and they realized prices of $14,750, $20,479, and $29,256. Just the year prior, a comparable Ploprof brought in $3,000 at auction. The Ploprof had taken an astronomical leap in value in the wake of Omegamania. The Omegamania auction has often been cited as an example of the impact of “hype.” The watches went on a world tour prior to the auction, and the unusually high results are suspected to be due to the hype and buzz generated by Antiquorum. Saori Omura, who is now head of HODINKEE’s vintage department, was working at Antiquorum’s New York office during Omegamania and says that indeed, “there is no denying that this thematic auction brought a new life to the Ploprof market.”  Ploprof prices remained relatively high immediately after Omegamania, with two examples in May selling for $14,750 at Antiquorom and $14,876 at Christie’s.

And then, the prices dropped. The average realized price for the Ploprof in 2008, among Antiquorum, Sotheby’s, Christie’s, and Phillips, was $8,453. In 2020, only three examples have come up for auction between the aforementioned auction houses. One passed, and two sold for $4,659 and $4,000 at Antiquorum. Longtime Omega collector and expert Bill Sohne remembers when one could routinely pick up the watch on eBay for $700-$900 in the early 2000s before Omegamania standardized a higher price point. He made sure to note that $900 was still incredibly high at the time for any vintage Omega other than the Speedmaster.

Does the Ploprof represent a good value today? Brandon Frazin, vintage manager at HODINKEE, thinks they’re “undervalued when compared to the prices of other dive watches that are less interesting and seen more in the market (basic Subs). The thing that is tough about the Ploprof is the large size, but they are surprisingly comfortable on the wrist.” It’s hard to determine what makes a watch popular among collectors, but one element is certainly historical significance, which the Ploprof has in spades. This author doesn’t find the watch entirely wearable or visually balanced, but that’s exactly why it’s so interesting. It’s a watch that starts conversations and ends the notion that every dive watch has to look the same. Additionally, most COMEX Ploprof examples were indeed used in the field, making provenance easy to confirm. If a COMEX Ploprof were to surface at auction in the future, an expert who wishes to remain anonymous speculates that it could bring in as much as $250,000.

Ploprof examples come up for sale infrequently, and according to a 2018 article from Fratello Watches, roughly 60% of Ploprofs coming in for service at Omega’s headquarters in Bienne have undergone a movement swap prior to being sent in for service. Finding an original Ploprof is increasingly difficult as time goes on.

When the “new” Ploprof was announced in 2009 (more on that later), Tom Nesbit saw at least two vintage examples a month come into his shop, Nesbit’s Fine Watch Service in Seattle, for restoration. This anecdotal observation is in line with the story the auction numbers tell, with a spike in interest during the relaunch.

But these days, he hasn’t seen one in at least a year.

“They’re relatively straightforward watches to restore; once you get the gaskets in the right order, it’s simple,” Nesbit says. “It consistently exceeds the 600m pressure test”

If a Ploprof comes in that has never been serviced before, it presents a slightly difficult scenario. It has been hermetically sealed for a number of decades, but the gaskets in the watch degrade and turn into a sticky goo that can damage the movement and ruin the dial. The dial is often referred to as the most important part of a watch, so utmost care must be taken when removing the old gaskets as to not damage the dial. Nesbit says the movement parts can go in the ultrasonic cleaner, but great care must be taken when cleaning the dial. As of writing, most parts aside from the middle case are available from Omega, making restoration a straightforward affair.

Some Ploprofs appear “backwards” with the crown on the right, in the orientation of standard watches, and Nesbit says that this is because the dial feet are symmetrical, meaning that the dial can be affixed to the movement in an upside-down orientation. Whether or not the watch ever came this way is a point of contention among Omega enthusiasts, but it’s certainly much easier to use the bezel lock in the standard configuration.

The Ploprof was retired in 1979, with a production run just short of a decade, but in that short time, it carved out an outsized reputation for itself as a real tool watch used primarily by the folks it was engineered for – a very specific watch designed for a very specific purpose, when watches were an essential part of the dive kit. Diving computers replaced watches, and the larger role of the wristwatch changed over the years. The Ploprof was very much a watch of its time, a time when the diving boom gave rise to a bevy of tools to conquer and explore the underwater world. When the production of the watch stopped in ’79, the innovation didn’t. After the Ploprof’s run, Omega was experimenting with deep-diving quartz models, and most recently, the Seamaster Planet Ocean Ultra Deep Professional.

But at Baselworld 2009, Omega brought back the Seamaster 600 Ploprof design. But this time around, it featured a few fundamental design changes, like a 1,200m water resistance rating, a screw-in caseback, an anodized metal bezel lock button as opposed to plastic, and a co-axial caliber 8500 inside. Visually, not much had changed from the original Ploprof, but by most counts, the watch was entirely new, and one difference stood out from the rest.

The original Seamaster 600 Ploprof was designed to be completely hermetically sealed so an HEV would not be necessary. The idea being that if helium never made its way in, it would never need a way out through a helium escape valve. When the 2009 Ploprof was released with a helium escape valve, it was a major point of contention, along with the watch growing a few millimeters.

Despite the controversial inclusion of an HEV, the modern Ploprof was a runaway hit, and our own Jason Heaton even owned one in 2010, diving with it in Sri Lanka, reporting that it was a “big old thing. Heavy and clunky to use for dive timing, if I’m honest. Incredibly well made though. The details were amazing.” And it certainly was heavy. The stainless steel watch weighed in at 279 grams. But in 2017, Omega did what it set out to do during the research and development phase leading up to the launch of the watch in 1971.

Omega produced the Ploprof in titanium.

Omega had experimented in the late ’60s with titanium, but just couldn’t make it affordable or able to be produced en masse. In 2017, the company figured it out. The stainless steel model remained in production alongside the titanium model, but the titanium model included the Caliber 8912 and eschewed the date in favor of a balanced dial. The mesh bracelet it came on was also titanium.

In the 1977 film Star Wars: A New Hope, swashbuckling space smuggler Han Solo famously assures protagonist Luke Skywalker that his spaceship, the Millennium Falcon, is fit to transport them off of Tatooine with the line, “She may not look like much, but she’s got it where it counts, kid.”

Not only does the case shape of the Ploprof loosely resemble the profile of the Millennium Falcon, what Han says about the ship is also true of the watch. It’s not conventionally beautiful, but it sure as hell had the technical chops to get the job done. It’s a watch that reminds us that, sometimes, design is an absolute function of a technical brief and aesthetics are secondary. The notion of a watch whose design is derived from the need to perform under extreme circumstances is so powerful that Omega even brought the watch back a second time in an era when technical divers don’t rely on mechanical watches anymore. And it remains in the Omega catalog to this very day.

Just a quick thank you to a number of folks I consulted during the research for this piece: Petros Protopapas, Omega’s Brand Heritage Director; the gentleman (who wishes to remain anonymous) behind www.omegaploprof.com; Bill Sohne, a fixture in the Omega scene; Johnny (@johnnyw_b), a passionate collector; and Nesbit’s Fine Watch Service in Seattle.