A very rare Omega 1st Gen 600 Professional Diver (Plonguer Professionel). Hard to find a 1st Gen especially in this original dial condition. Another grail for me. I am happy.

Reference: ST 166.0077
International collection: 1970 - 1979
Movement Type: Automatic (mechanical)
Caliber number: 1002, Created in 1968, 20 jewels, Central sweep-second hand
Functions: Date
Case: Stainless steel
Dimensions: 13,5 x 55 mm
Case back: Unishell (case opening on dial side), Full metal
Dial: Navy blue or black, with super-luminous hour markers and super-luminous hands (tritium) insuring perfect legibility even at great depths. Minute hands (most useful ones when diving) are super large-sized and are off set by a fluorescent orange border
Crystal: Mineral
Bracelet: Isofrane
Water resistance: 600 meters

MORE INFORMATION
Ultra-resistant and super water-resistant watch for professional divers, from which it gets its name ("plo" comes from "plonger" which means "to dive" in French; "prof" comes from "professionnel" which means of course "professional").Tested to 600 m at the factory and to 1'000 m in the Gulf of Lion off the coast of Marseilles, it was notably used by Commander Cousteau during a series of experiments designed to test man's physical and psychological capacities to work at depths of around 500 metres. In 1970, in operation "Janus", it spent 4 hours a day for eight days on the wrist of 3 divers from COMEX, an oil research firm which was exploring the sea floor (250 m depth) in the Gulf of Ajaccio.

Case : asymmetric (13,5 x 55 mm), protected crown with locking screw at 9 o'clock to allow the wrist to move freely(requiring 2 hands to unscrew it) and to avoid accidental manipulation.

Bezel : bi-directional black stainless dive notched bezel ("0-60" scale, luminous) locking by a red push-button (between 1 and 2 o'clock).

Case back : Flat back with circular addendum with anti-slipping mechanism.

For isofrane straps of 24 mm lug-size (synthetic rubber with high chemical and mechanical qualities), in blue (ref. ST 4750/055), red (ref. ST 4750/155) and yellow (ref. ST 4750/176), or black corfam strap (ref. ST 0793/003) . Also for stainless steel milanese bracelet with coat of mail (ref. 1162/162 or 1266/237-240).

Crystal : Monolytic chemically-soaked mineral crystal treated with anti-reflective and anti-abrasive material pressed to 120 kg, then held on the gasket by a screw-in ring.

Water resistance : Internal and external water-resistance system proven by a helium leak detector.

International Collection : 1970-1979

Swiss retail price (1973) : CHF 690.- (on isofrane strap) or CHF 720.- (on SS milanese bracelet).

As this model's dial can be shifted by 180 degrees, sometimes these pieces can be wound up incorrectly during repairs by a careless repairer or who mistakenly thinks that it is done correctly by positioning the crown at three o'clock. Doing this moves the (red) locking push piece of the turning bezel to seven o'clock , making the latter very difficult to move using a single finger !
The Ploprof would be scrupulously analysed by the American diving research centre Ocean Systems Inc. in Tarrytown, NY, which concluded that, taking into account the appropriate proportions, the timepiece is more resistant than a submarine!

(Information courtesy of Omega Vintage Information @ www.omegawatches.com)