Omega PloProf
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Omega Seamaster Professional 600m/2000ft
Throughout the 1960s the sport of Skin Diving (now more usually known as Scuba Diving) had been developing. The equipment and tools for this sport developed from the military and commercial need to work in the oceans and seas around the world. This commercial need, in industries such as Oil and Shipping, created organisations of Professional Divers. One of the major diving operators of the time was Comex who, as an oil research firm, needed tools that their Diver's lives would rely on. In those days computers that could calculate the needs of a diver like the wrist mounted dive computers of today would have taken up a whole room, so the divers relied on the one mechanical device from which most of the risk factors of their dive could be mentally computed, a watch. The watch makers recognising this need, jumped headlong into the fray to build an ‘ultra water-resistant’ (sometimes termed ‘super water-resistant’) watch for Professional divers and so watches like the Rolex SeaDweller and the Omega Seamaster Professional 600m/2000ft were born.
The PloProf is a modern sized watch. Whereas many vintage dive watches tend to err on the small side for modern tastes, that is not the case with this one. Today's trend is for larger watches and the PloProf holds its own in the modern world, matching visual clues and history in the same fashion as modern offerings from the likes of Panerai.
These watches are now 35+ years old, but you really wouldn’t guess that from the quality of the workmanship. Whereas many vintage watches can feel a little cheap against the modern options, the PloProf is easily on a par with high quality watches sold today. The asymmetric Monobloc case is solid, heavy and made of high grade stainless steel. With its protected crown, locking screw and red button it often causes a stir with people who have never seen such a watch in the metal.
Developed in conjunction with Comex and the legendary Jacques Cousteau, Omega conceived and developed what was probably the first waterproof watch designed and built solely for the diving professional.
The watch took 4 years to come to the market after extensive testing and arrived in 1970. It was nicknamed PloProf by the French speaking development team and derives from the French term PLOngeur PROFessionnel (Professional Diver).
Comex used early models of the PloProf and continued their research into living underwater for prolonged periods. One Issue that still concerned Comex was helium infiltration, which carried the danger of causing a watch crystal to pop out during decompression. There is no proof that this problem occurred with any Ploprof, and later tests by the American diving research centre Ocean Systems Inc. in Tarrytown, NY, certified that the Ploprof was ‘more watertight’ than a submarine. However, Comex wanted to be sure to combat the helium infiltration issue, rather than trust improved watch-case sealing. They chose to continue their research work with Rolex and Doxa to test their new Helium Expulsion Valve (HEV) designs. HEVs were incorporated in the Rolex SeaDweller which Comex used reliably for many, many years.
The large bezel ‘insert’ is made of acrylic poured into the stainless steel bezel. The luminous indices on the bezel make for one of the best, and largest, luminous effects when viewing in the dark. Sadly, the luminous material on these bezels is most likely Tritium and its luminance is not long lived these days due to Tritium’s ageing. Also, whilst the acrylic gives a deep black classy look to the bezel, it is not really the best choice of material.
Knocks and poor watchmaker’s attempts to lift the bezel can cause cracks and lifting of the acrylic into which water can penetrate. One bonus is that scratches are easily polished out.
There are numerous PloProf bezel variants and these are discussed in another article on DeskDivers {here}.
The thick chemically hardened mineral crystal which is treated with an anti-reflective and anti-abrasive coating is compressed onto its gasket within the case to 120 kg by a threaded locking ring. The crystal sits slightly below the bezel and is thus protected by its edges.
The case back is flat with a raised circular portion of anti-slip grooves almost 1mm tall which help keep the watch in place on the wrist.
There are two case variants of PloProf. The C and U models, and these will be discussed in a future Deskdivers article. Please keep checking back as we hope to bring you that article in an update soon.
The drilled lugs make for easy strap changes and allow the use of shoulder-less spring-bars for added security when diving.
Whilst the Monobloc case was an innovation at the time, it has been used subsequently by other manufacturers (e.g. Tag Heuer in the 1000m, Jenny in their Caribbean range). However, there are two unique characteristics that distinguish the PloProf from all other watches:
The first is a Bezel lock. The bi-directional bezel can only be moved if the red button is pressed at the same time.
This seems unwieldy at first but is actually simple and easy to use when on the wrist using a single gloved hand.
Usually, the inclusion of a bi-directional bezel would raise a sneer from dive watch aficionados but with the PloProf’s locking mechanism there really is no need to worry about the accidental movement of the bezel during a dive and so there is no need for it to move solely anticlockwise. By being free to move either way, it is easier and quicker to set.
Not long after the introduction of the PloProf in 1971, Omega launched the Seamaster 1000m (case Ref. 166.0093) which used some of the PloProf’s technology elements (i.e. it's bezel, dial, minute hand and Monobloc case) in a more conventional case style. This helmet-shape case is known as the Flightmaster style of case, as this form was initially used for the Flightmaster chronograph. The 1000m used a conventionally styled crown, with crown guards, and soldiered on in the Omega range until 1982.
Similar in design was the prototype Seamaster 1000m Megaquartz, which it would appear was also tested by Cousteau, photographs exist to prove this, but did not become a widely sold model.
Sadly the main design elements of the PloProf (crown protection and bezel lock as discussed below) were never to be seen again on an Omega and even the Monobloc case seems to have been neglected once the Dynamic range was dropped from the catalogues at the end of the 1970’s.  Perhaps Omega had other issues at that time and the expensive designs of yesteryear needed to give way to simpler and cheaper materials and designs during the quartz age.
During the 4 year gestation period the PloProf was tested to 600m at the Omega factory and to 1000m in the Gulf of Lion, off the coast of Marseilles. It was used by Commander Jacques Cousteau during his series of experiments designed to test man's physical and psychological capacities when working at depths of 500m.
During ‘operation Janus’ in 1970 3 Comex divers wore the watch at a depth of 250m for 4 hours a day, for eight days whilst exploring the sea floor in the Gulf of Ajaccio.
The watch was very expensive and the top of Omega’s range at the time of its launch. It is unclear, and unlikely, that Omega recouped its development costs in the model’s life-span between 1970 and 1979. The watch was a hit with professional divers but its price, approximately twice that of a Rolex Submariner, kept many hobby divers away. For information the Swiss retail price in 1973 was CHF 690 on isofrane strap, and CHF 720 on Milanese bracelet (known these days as ‘mesh’). These factors mean that today these watches are reasonably rare.
Does the PloProf ‘work’ in the modern world? Well… Women find it ugly and men find it beautiful! However, men do seem to be entranced by objects that are large, technical and contain blue and orange elements. There is a distinct air of industrial design about the watch that fits well with current trends.
The crown is a bit of a curates egg – that is to say; ‘good in parts’. It is a joy to screw and unscrew, but is a little fiddly to set the time/date due to the square edges. When closed it forms a flush fit with the case and will not unscrew in use.
Interestingly, Omega must still have been at the final design stage when the advertisements were produced for the watch and publicity photos show the Ploprof with the prototype’s red crown screw.
The red plastic bezel pusher is simple and easy to operate one handed, but does tend to pick up nicks and marks from use, although these pushers are readily available these days and simple to replace.
The dial of the PloProf was available in at least three variants over the production run, these (and the two types of hour hand) are dealt with in a separate article {here}.
Suffice to say the dial and hands are crisp and clear and obviously designed with one thing in mind – to tell the time instantly when under water. The hour hand melts into the background when diving and instantly the diver can see the large bright minute hand, and assess elapsed dive time. On land the simple dial and large watch ‘face’ are a joy to behold, the blue of the dial working well with the orange and white hands.
Secondly, the innovative crown locking mechanism. The crown itself, which on first observation would appear to be the familiar looking splined cylinder,acrylic is actually the square end plate. The splined cylinder in reality is a crown locking nut. The square crown is screwed in/out using the splined nut (the splines aiding grip) which remains where it is located in the case. The linear movement of the crown mechanism compresses the crown seals directly without the distortion and wear created when using the more usual twisting motion of a conventional crown, forming a long lived seal. The crown when screwed in also forms a flush fit with the case, effectively protecting the watch against impacts or snagging. The Ploprof might well have the most effectively designed and engineered crown protection and seal system ever built. Only the Panerai crown comes close to these design traits but is potentially less water secure due to its over-centre lever action meaning it is not adjustable once the mechanism and seals become worn.
The case is large and whilst the watch wears low on the wrist it does seem to enjoy confrontation with fridges, door jambs and other items of everyday life. Over time, these deflections tend to pepper the bevelled edges of the case and give the watch a great patina.  Although, it is worth noting that Omega Bienne (and some other Omega approved restoration houses) can refinish the watch to ‘as new’ condition if required.
It is worth noting that Omega at Bienne is the one place that any PloProf should be sent for servicing or restoration work. Omega, themselves, control the flow of parts for these watches and should be the first choice for any remedial work. Omega have taken their history seriously and are prepared to help keep their old models running. Well done Omega!
The PloProf’s dial feet are placed symmetrically which means that the dial can be fitted either way round i.e. a 180 degree switch.
Sometimes these watches can come back from a service in a different configuration to the way they were sent.
Careless repairers sometimes assume that the crown should be at the usual three o'clock position.
With this change made, the bezel locking mechanism (red pusher) moves to seven o'clock, necessitating the use of the thumb to depress it and therefore making the bezel very to awkward to move using only the fingers. With this in mind it would be good practice to mention crown orientation in any service instructions.
The in house Omega 1002 movement is not one of the most attractive Omega movements (although, of course, only watchmakers ever get to see it!) but is solidly built and long lived. It is capable of keeping very good time and spare parts are available for servicing and repairs. One great feature of this movement is the quick set date which allows the date to be set both forward and backwards – when using this feature it makes you ask yourself why all watches can’t do that?
Flightmaster style bracelet – The usual lightweight Flightmaster style bracelet from this era and not the favourite choice of owners today due to its rather flimsy thin construction (ref-1162/162/1).
Planet Ocean Rubber Strap – Omega now bill this as the modern PloProf replacement rubber Strap.  It is well made, has the looks of the Isofrane and wears very well.
The PloProf was available with a number of bracelet options.
Mesh - Among the most popular bracelets is the Mesh or Milanese (ref-1162/162 or 1266/237-240). These are constructed from a 4mm thick stainless steel mesh that suits the 70’s Omega watches perfectly – they look like they would match your chain-mail shark-proof suit when diving! These bracelets have an airline seat belt style clasp and are very comfortable to wear.
It is worth noting that in standard form even on a large watch like the PloProf, the mesh bracelets are best suited to those with slim wrists. For gorillas an inch long extension is available. These can be fitted on either side of the clasp and also daisy-chained if need be.
Comex Divers Extension - referred to by Omega as “the offshore bracelet for waterproof watches“
(Ref-1247-1266/02). It is a flexible black Adiprene extension piece for the mesh bracelets. This distance piece can very quickly and simply be sized to different lengths when preparing for a dive as it has ridges that can be pulled through the clasp and clamped tight.
Leather - Due to the PloProf’s 24 mm lug-size many of the after-market handmade Panerai style leather straps can be utilised.
•    Stainless Steel Monobloc case – Omega Ref. 166.0077 / 166,077
•    Bi-directional rotating locking Stainless Steel bezel
•    Tritium luminescent hands, hour markers and bezel
•    Antireflection coated mineral glass
•    Screw down captive crown
•    Black on silver Date display at 3 o'clock
•    Self-winding Omega 1002 movement with 20 jewels
•    Water resistant to 600 meters (2000 ft.)
•    Width: 54mm
•    Length: 45mm
•    Weight: approx. 175g with mesh bracelet
•    Thickness: 15mm
•    Crystal/Dial width: 29.4mm
•    Bezel width: 44mm
•    Lug width: 24mm
Movement Specifications:
•    Debut 1968
•    ø Dm= 27.9mm, H= 4.25mm
•    20 Jewels
•    28800 A/h
•    Power reserve approx. 40 hours
•    Quick set date – bi directional
•    Hacking
Corfam - Originally Omega offered a black corfam strap (ref. 0793/003) which Omega reasoned were useful for wearing on land as Corfam is a synthetic leather and not water resistant.
Isofrane - the original PloProf waterproof strap which is made of synthetic rubber with high chemical and mechanical resistance.
These were available in; black, blue (ref. 4750/055), red (ref. 4750/155) and yellow (ref. 4750/176)
For further reading we would highly recommend the book... Omega PloProf by Jon Wallis for the most comprehensive and in-depth information on the PloProf.
The Ploprof case patent (CH480680) was registsred in 1967 and the cases were manufactured by Schmitz Freres in Grenchen, Switzerland (denoted by the SF stamped on the inside of the caseback). In the early days Schmitz Freres was asked to manufacture prototypes of these cases in Titanium. This was done as the design team considered that the Ploprof case was both large and heavy and that using Titanium, which is at 40% lighter than stainless steel, would make a difference to the wearer as at the time most watches were considerably smaller than the Ploprof. SF made only 10 prototype Titanium cases, and stopped production due to difficulties in the machining of Titanium (it is very strong) and also due to the cost of the raw material.
In the contemporary advertisements, Omega made much of the depth testing on these watches, both in the field but also in the lab.
The cases were routinely hydrostatically tested to 60ATM and shock tested (500g weight dropped onto a running watch from 25cm).
In one test the watch was taken down to 1370m using hydrostatic pressure and it was reported that it only stopped at that 'depth' as the crystal had deformed to the extent that it was resting on the seconds hand, so stopping the watch from running. Interestingly, this failure can be partially attributed to the design of the case sealing, which whilst superior for the advertised 600m rating, would not be correctly designed if going beyond 1370m.
Looking at the design, the crystal rests on a large ring 'insert' (actually made of two interlocking parts - one being plastic, one steel) that in turn rests upon a seal against the back of the watchcase. When the crystal is fitted it, the ring and seal are compressed and the seal squashes to isolate the case interior. However at great depth there is extreme pressure and this arrangement can continue to compress as the seal (and to some extent the plastic part of the ring) is by nature not solid. This has the effect of moving the crystal closer to the hands. Had that insert been made of one solid piece of steel and be resting on a machined surface at the back of the watch, then the Ploprof would undoubtedly have been able to achieve a greater depth. When you read that, do you recognise the design we've just outlined? Yes its called a Rolex Sea Dweller Deep Sea.... Its nice to see Rolex basing the new model of their original Ploprof competitor on the original Ploprof design, what goes around....
The Locking nut Patent (number CH503310) was filed on 23rd Oct 1968 but not published until 1974. Interestingly we often see these in red in early models and that is because these were originally manufactured from a synthetic material. Omega found in early testing that this material was not suitable and the nut was very quickly replaced with one made from stainless steel.
One of the longest running debates in the PloProf world has been about the datewheel. As mentioned above, because of the symmetrical dial feet, the dial can be mounted on the movement with the stem on either the left or the right. The question is whether the same datewheel can be used or is there a specific datewheel for each configuration? In fact the answer could have been deduced by pure logic, but in the name of science DeskDivers dismantled a PloProf to settle this issue once and for all.
So to end the speculation... There are two datewheels. The date wheel used on the Ploprof is a special calibre 1002 part that is only used for watches with the crown at 9. Initially you would think there would be no difference between a 9 or 3 date window, there is and this can be demonstrated using the movement from a ‘destro’ PloProf which is equipped with the standard 1002 datewheel.
3 o’clock stem and all is well.
The secret to solving this conundrum is down to symmetry. The number of days on the wheel (31) is not evenly divisible so the date can only be centred in the window in one configuration. Comparing the 2 pictures it becomes clear that if a person wished to repair a Ploprof using a donor 1002 movement they would need to obtain the 'special' PloProf cal 1002 date-wheel.
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