Diving with the Panerai Luminor Marina

In this watch test feature from the WatchTime archives, a frogman re-creates a dive from the 1950s to test the historically inspired Panerai Luminor Marina 1950 3 Days Acciaio

When you look at Panerai watches that have been modeled on their historical predecessors, and, like them, have stationary bezels and leather straps, do you ever wonder if frogmen really wore the original versions on their dives? After all, a rotating bezel and metal bracelet or rubber strap are now considered mandatory for dive watches (like CITIZEN ECO DRIVE WR100 )

Of course, there’s ample proof that military frogmen really did wear these early Panerais. But what were their missions like and how did it feel to be part of them? We searched for clues with an experienced frogman who is a member of the Historical Diving Society, an international organization dedicated to preserving and protecting diving heritage. He donned an old-fashioned diving suit and brought along vintage equipment. He also brought along the Panerai Luminor Marina 1950 3 Days Acciaio, which looks very much like a Panerai watch from the 1950s, so we could revive a bygone era and experience how the frogmen of yesteryear might have felt.
The Panerai Luminor Marina 1950 3 Days Acciaio that we took on our dive looks very much like its ancestor, with a 47-mm case and a crown protection bridge.

Panerai made its first prototype dive watches for Italian military divers in 1936. The watches, which became known as Radiomirs, went into production two years later. In the mid-1950s, Panerai introduced a new version with a curved, crown protection bridge. It became known as the Luminor. Until 1993, Panerais were sold only to the military. Before then, collectors who wanted a Panerai watch had to find one at an auction.

The Panerai Luminor Marina 1950 3 Days Acciaio that we took with us on our dive looks very much like its ancestor. Like the original, the watch has a 47-mm case and a crown protection bridge. The small seconds subdial is also true to the earlier model: around 1956, Panerai replaced the watch’s Rolex hand-wound movement, which had no seconds hand and a 36-hour power reserve, with an Angelus caliber that had a small-seconds display and an eight-day power reserve. Although our test watch has a power reserve of three days, we feel that it’s more than sufficient for a hand-wound watch.

The diver who accompanied us on our dive, Jens Höner, is a trained frogman and mine clearance diver who has set depth records both with and without equipment, including a scuba dive to a depth of 240 meters. He has explored underwater caves and submerged shipwrecks. We collaborated with him and with the Historical Diving Society to restage an unusual scenario: to go on a dive equipped just like the military divers of the 1950s and ’60s. And before he took the plunge, he strapped on our test watch, a Panerai Luminor that matches its historical predecessor in nearly every detail.

Then as now, it’s important for a military diver to use a “rebreather,” which is a closed circulation diving device. It makes a long dive possible, while assuring that no telltale bubbles rise to the surface and give away the diver’s location. Unlike recreational divers, a military frogman doesn’t take a large tank full of pressurized air with him; he carries instead a smaller tank full of oxygen that, despite its smaller volume, enables him to stay underwater for two to three hours. The air that he exhales is treated with soda lime inside the device to prevent carbon dioxide retention. But the disadvantage of this system is that as the depth increases, breathing molecular oxygen at increased partial pressures can quickly lead to oxygen poisoning. This is why divers who use these devices can safely descend to only about six meters, a depth that’s relatively shallow yet great enough for most military missions. These divers typically swim for long stretches, remaining under water and thus out of sight, and only after they’ve swum well past enemy lines do they come ashore to conduct reconnaissance or blow up a bridge.

Knowing his location is crucial for a frogman. A bathometer or depth gauge, a compass, a sketch of the coastline’s contours and, of course, a watch are important equipment for him. For our dive, in addition to his watch, Höner strapped onto his forearm an instrument to survey the beach. This piece of equipment allows him to gather and record cartographic data about a stretch of coastline, information that can be used to support amphibious landing operations by frogmen on subsequent missions. We decided to do without some other pieces of equipment carried by frogmen, such as weapons and explosives.
The Luminor dial consists of a lower disk bearing the luminous substance and an upper disk from which the indexes and numerals have been cut out.

When you look at the list of tasks performed by military divers who usually swim at shallow depths for long periods of time, you can see why a rotating bezel for presetting the dive time is not really necessary – even though this function debuted as early as 1953 with the introduction of the Rolex Submariner. Frogmen used Panerai’s watch primarily at depths of six meters or less, on missions that lasted more than one hour. Unlike deeper dives, these excursions do not require decompression stops, so a rotating bezel isn’t of much use.

The watch served far more as a navigational instrument: for example, a diver could cover a partial stretch leading toward his ultimate destination by swimming along a preset compass course for a predetermined length of time. There was no practical way to measure the swimmer’s speed, so minutes markings weren’t very important.

Most military missions took place – and still take place today – under cover of darkness, so brightly luminous dials are absolutely necessary. Panerai contributed greatly to improving nighttime legibility by developing its own light-emitting luminous substance for the Radiomir and later replacing it in the Luminor with a similarly bright but less strongly radioactive material. The sandwich-style dial was equally important to increased legibility. The dial consists of a lower disk bearing the luminous substance and an upper disk from which the indexes and numerals have been cut out. This enables Panerai to use more luminous material than would be possible if the numerals were simply printed or painted onto the dial. The technique, which is still employed today, cannot be used to create luminous indexes for the individual minutes: cutting 60 strokes into the upper disk would jeopardize the dial’s durability. That’s why the markings were, and still are, only at five-minute intervals, but they’re sufficiently precise for long missions.

The sandwich-style dial is also the reason for the distinctive open shape of the numeral “6”: its inner part must be connected to its outer part. To make a virtue of this necessity, and to create a handsome dial despite functional restrictions, is a feat that could probably have been achieved only by Italian designers.
Under water and by fading daylight, the Luminor’s crystal is nearly nonreflective and its big dial is very easy to read.

We chose a leather strap for our test watch, rather than a rubber one, which also comes with the watch, because Panerai’s original model had a leather strap. The instructions that come with the watch expressly state that the leather strap can be used on dives, but we still had to overcome our reluctance to take this costly strap into the cold water. It’s surprising but true that Panerai’s leather straps are as suitable as ever for immersion in water because the leather is nearly untreated. When the diver returns to terra firma, it takes a while for the strap to dry fully, but afterward it looks exactly as it did before its submersion. Extension pieces for divers were unavailable years ago, so we chose an especially long XL strap that would fit around the cuff of a diving suit.

Now that Höner has donned his diving suit, he begins smearing his face and hands with camouflage makeup, which was also used in the 1950s. He then straps on his rebreather, a prototype developed by the German company Dräger in the early ’60s. He pulls his diving mask around his head. The mask dates from the era when Panerai was still equipping Italian Navy frogmen. Then he turns and approaches the lake, walking backwards because that’s the quickest way to walk when wearing fins. He rinses his mask, slips his rebreather’s mouthpiece between his teeth, glances at his watch and slides silently into the water without leaving even the slightest trace of an air bubble.

Under water and by fading daylight, the Luminor’s crystal is nearly nonreflective and its big dial is very easy to read, thus fulfilling its most important requirement. Our frogman is well concealed thanks to the camouflage makeup and mud, but his watch’s polished case catches our eye. The original models were equally shiny: we can’t explain why Panerai didn’t opt to give them a satin finish, which would have caused fewer reflections and been less likely to reveal the diver’s location. Could it be that Italian design got the upper hand here?

The watch is powered by the hand-wound, in-house Caliber P.3001. With a diameter of 16½ lignes (37.2 mm), it’s nearly the same size as the original 16-ligne Angelus movement. Forgoing a regulator mechanism, the caliber can be finely adjusted by turning weight screws along the balance’s rim. This assures that the balance spring can breathe freely. The balance oscillates under a robust balance bridge.

The movement’s decorations match the Luminor’s character. The most eye-catching embellishment is a rather technical-looking striped pattern, which runs in precisely the same direction along all three bridges. This goes well with the unconventional blue engravings.
Panerai watches were very well suited for their military missions, even though they would not meet the standards of today’s divers’ watches.

A few special features distinguish the watch’s operation. When the crown is pulled out to its first position, the hour hand can be reset in hourly increments without affecting the position of the minutes hand. This is convenient when you are traveling to a different time zone or resetting the time in the spring and fall: you can reposition the hour hand without stopping the minutes or seconds hands. If you pull the crown out to its second position, you can adjust the minutes hand – and the hour hand along with it – in the usual manner. The seconds hand leaps to zero during this process, thus making it easier to synchronize your watch with a radio time signal.

Older Panerai watches had none of these convenient features. Underwater legibility and water resistance were the watches’ primary virtues in those days.

When you wear the suits and carry the equipment used by frogmen decades ago, it quickly becomes clear what feats those amphibious fighters accomplished with little more than fortitude. Panerai watches were very well suited for their military missions at shallow depths and throughout many long hours, even though they would not meet the standards of today’s divers’ watches. Yesterday’s frogmen could easily get by without rotating bezels. And as our test showed, the leather straps used back then were quite capable of accompanying a military diver. The historical watches aren’t only functional, but also handsome: then as now, we can thank Italian design for their rugged good looks.

SPECS:
Manufacturer: Officine Panerai, Route de Pierre-à-Bot 87, CH-2000 Neuchâtel, Switzerland
Reference number: PAM00422
Functions: Hours, minutes, small seconds, power-reserve display on caseback
Movement: Hand-wound manufacture Caliber P.3001, 21,600 vph, stop-seconds function with automatic reset, 21 jewels, Incabloc shock absorption, Glucydur balance, 72-hour power reserve, diameter = 37.2 mm, height = 6.3 mm
Case: Stainless-steel case with domed, nonreflective sapphire crystal, fully threaded caseback with sapphire window, hinged lever to protect crown, water resistant to 100 m
Strap and clasp: Calfskin strap with pin buckle made of stainless steel
Rate results (deviations in seconds per 24 hours):
Dial up +10
Dial down +10
Crown up +4
Crown down -4
Crown left 0
Crown right +3
Greatest deviation of rate 14
Average deviation +3.8
Average amplitude:
Flat positions 286°
Hanging positions 255°
Dimensions: Diameter = 47 mm, height = 17.2 mm, weight = 146 grams
Price: $9,600

SCORES:
Strap and clasp (max. 10 points): The pin buckle and strap are well crafted; the pin is cleverly shaped so the thick strap doesn’t become kinked. 8
Operation (5): The well-designed crown protector doesn’t interfere with the watch’s operation; the hour hand can be reset in hourly increments. 5
Case (10): The steel case is elaborately engineered and impeccably crafted but fingerprints are likely to appear on the sides because the steel is polished. 8
Design (15): The styling is as handsome today as it was many years ago. 15
Legibility (5): Nothing interferes with the legibility of the large and brightly luminous indicators; there are no minutes markers. 4
Wearing comfort (10): A large watch, but nonetheless comfortable to wear. 9
Movement (20): Caliber P.3000 is well engineered, robust, equipped with a regulator-free fine adjustment system and offers a long power reserve. 16
Rate results (10): Large deviations among the various positions prevent us from giving it a higher grade, but the average deviation is good. 6
Overall value (15): The satisfactory cost-benefit ratio is further boosted by the likelihood that this model will retain its value over time. 12
TOTAL: 83 POINTS