IWC Schaffhausen GST Deep One Diving Watch (1999)

Introduced in 1999,The IWC GST Deep One diving watch was the only one of its kind to feature a mechanical depth gauge, maximum depth display and a rotating bezel to show dive time.

The GST Deep One ingeniously combines the two parameters crucial to anyone fascinated by the sub aquatic world: dive time and dive depth. Entirely mechanical, it is a superbly finished watch ideally suited to the rigours of amateur scuba diving.

IWC Schaffhausen GST Deep One Diving Watch (1999)

The Deep One is tested for water resistance to 100 metres. But there is a very good reason why the depth gauge is calibrated to show exact depths to 45 metres: the world’s major diving associations recommend that the maximum depth for safe amateur diving is between 30 and 40 metres.
IWC Schaffhausen GST Deep One Diving Watch (1999)
The Deep One is the product of an amazing feat of engineering. As in the Ocean or the GST Aquatimer, a special titanium alloy was the material chosen for the case. This is as voluminous as it is complex and houses two completely independent systems.

The Deep One from IWC is first and foremost a watch with a precision mechanical movement and is ideal for timing the length of a dive. To do so, one simply turns the rotating inner dive ring until zero aligns with the minute hand. The time spent under water can then be read off on the ring. The mechanical depth gauge in the centre starts functioning from the moment the diver submerges. The depth gauge has an additional hand, which functions as a maximum depth indicator and remains in position to show the maximum depth reached during the dive, while the depth gauge itself returns to zero when the diver leaves the water.

The automatic movement, the ultra precise IWC 8914 calibre, was chosen because its decentralized small seconds hand leaves sufficient room for the depth gauge axis in the centre of the watch. The movement itself is somewhat smaller than the Deep One’s considerable 42 mm external diameter.

The reason for this is that the pressure exerted by the water is not measured on a membrane attached to the back – as was the case in the few wristwatches produced in the past with mechanical depth gauges – but via a ring-formed measuring device inside the case. This runs around the movement in a separate part of the case. The mechanical expansion of this element caused by water pressure is transformed into movement of the depth gauge by a system of levers and wheels.

The water exerts pressure on the gauge after entering the watch through an inlet valve at the 4 o’clock position, which also serves as the adjustment for the depth gauge.

A testing cylinder supplied with the watch and applied via the inlet valve can be used to verify that the depth gauge is functioning correctly. The actual crown can be screwed in and is used for setting the time, the date (via a rapid-advance mechanism) and for starting the movement. To facilitate accurate setting of the movement, the watch is equipped with a stop seconds hand.

The third crown at the 2 o’clock position fulfills two important, diving-linked functions. As we have already seen, it can be used to turn the rotating inner ring to display the exact diving time, but only in the “save” direction – i.e.\ anti-clockwise.

Apart from this, the crown can be pressed down to reset the maximum depth display. Outer protection is provided by a convex, 3.2- mm-thick sapphire glass. To make the watch even safer in practical use, critical display functions, such as parts of the rotating dive ring, the minute hand and the depth gauge, are luminous.

Technical details


Date at 3 o’clock
Measures length of dive and depth to 45 m

Diving-functions crown at 2 o’clock
Pressure-measurement crown at 4 o’clock
Water-resistant to 100 m

Rotating ring (measures length and depth of a dive)
Small seconds at 6 o’clock

Titanium + Velcro strap for wearing it on a diving suit

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