The first wristwatch termed “waterproof” produced by IWC wasn’t meant for diving. It was produced in 1945 under a British military contract as a “W.W.W.” – an abbreviation for “watch, wrist, waterproof”.
Collectors frequently use the misnomer “Mark X” for this watch, and it wasn’t actually waterproof. It was really more “water-resistant”. Unlike the other so-called “Dirty Dozen” military W.W.W. watches, IWC uniquely used a snap-on case back with a lead inner sealing ring to increase water resistance. No specifications are known, but its water-resistance probably was only to about 10 meters.
The first true IWC water-resistant wristwatch arrived more than two decades later, with IWC’s Aquatimer model in 1967. That classic watch, reference 812 AD (re-designated as 1812 in October 1971) had a water resistance to 20 atmospheres, about 650 feet. It used a rotating internal bezel and two crowns, one of which operated the bezel.
Two years later, a second Aquatimer model was introduced as reference 816 AD (later 1816). It had shaped cases and striking “shadow” dials, as well as greater water-resistance to 30 atmospheres. In the late 1970s, this model was succeeded by reference 1822.