Taking the Field: Omega Seamaster Ploprof 1200M It is water resistant to 2,000 meters and is equipped with self-winding in-house Caliber 80110. The IWC Aquatimer Automatic 2000 has a titanium case. But titanium is an even better choice for watch cases because this metal is totally impervious to corrosion by saltwater. The submarine steel that Sinn uses for its divers’ watches has a PRE value of 38.
Rolex’s cases are made from 904L steel, which has a PRE value of 35, and is quite resistant to corrosion by saltwater. These cases should always be rinsed in fresh water after exposure to seawater. Most steel cases are made from 316L steel, which has a PRE value of only 24. Higher PRE values provide greater resistance. Steel’s ability to resist corrosion by saltwater is measured by its PRE value: PRE means “pitting resistance equivalent.” A PRE value of 32 is considered to be resistant to corrosion by seawater. The case can become speckled with tiny holes, behind which lurk larger cavities. Saltwater can cause pitting in the surface of a watch’s steel case. Brawn in the Brine: IWC Aquatimer Automatic 2000 This 42-mm watch is water resistant to 300 meters. Ball’s self-winding caliber, which is based on Sellita’s SW 200, is COSC-certified. Ball Watch uses another patented system to modify the shock absorbers for the balance so the watch is more resistant to vibrations. A patented system protects the crown against impacts. Ball Watch uses this technique in its Engineer Hydrocarbon Black, which has a titanium case coated with black DLC, a scratch-resistant ceramic bezel and a 5.3-mm-thick sapphire crystal. Watches equipped with these luminous tubes are frequently used by the military and by members of the Special Forces. The tubes continue to gleam brightly, even after spending years in total darkness. Here, little glass tubes are coated with a luminous substance on their inner surfaces and filled with safely captured tritium, which activates the luminescent material that lines the tubes. This is not the case when the dial’s illumination relies on tritium gas. Some watches can be read after eight hours in darkness, but even Super-LumiNova gives up the ghost if the gloom lasts much longer. When nighttime legibility is at stake, everything depends on how long the dial’s luminous material continues to glow. A watch designed for extreme missions must be easy to read in every situation.
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