IWC Portuguese Chronograph Classic Automatic Stainless Steel Men's Watch IW390404

Following on from the GST Deep One (Ref. 3527) in 1999 and the Aquatimer Deep Two (Ref. 3547) in 2009, IWC Schaffhausen is now rolling out its third generation of diver'swatches with a mechanical depth gauge. The Aquatimer Deep Three (Ref. IW355701) is a perfect example of watchmaking evolution from Schaffhausen. The watch's development can be traced simply by comparing the three different concepts used for the rotating bezel system that keeps track of dive time. The GST Deep One was fitted with an internal rotating bezel that was set using a crown at "2 o'clock". This technically advanced solution made it practically impossible to move the time of the start of a dive by accident. In addition, the scale under the glass, with its sensitive luminescent coating, was perfectly protected against water,dirt and scratching. However, it was not easy to wind the crown wearing diving gloves or under poor visibility conditions. For this reason, IWC's 2009 Aquatimer collection came with an external dive time ring that could easily be rotated, even with gloves, and only anticlockwise, for safety reasons. The ring consisted of several parts and featured an inset four-millimetre-wide sapphire-glass ring, the lower surface of which was coated with Super-LumiNova®. 

The case design of the Aquatimer Deep Three combines the advantages of the internal rotating bezel - such as protection of the scale against dirt and scratches - with the convenience of the external rotating bezel. It has been made possible by an IWC invention: the sophisticated sliding clutch system transmits the rotations of the bezel to the interior of the case and the internal rotating bezel. Here, too - for safety reasons and thanks to the IWC SafeDive system - the internal rotating bezel, which engages in precise one-minute intervals, can only be moved anticlockwise.

Highlighting the Depth Gauge
The mechanical depth gauge is the technical highlight of the Aquatimer Deep Three, which is pressure-resistant to 10 bar. In the 1990s, the GST Deep One in titanium was one of IWC's most ambitious technological projects ever. Diver's watches with mechanical depth gauges were a rarity at the time, and electronic meters ruled the market. The case design, sealing system and metering mechanism all seemed far too complex for mechanical diver's watches. However, IWC's engineers did not shy away from the difficulties. They equipped the GST Deep One with a calibrated pipe, which ran around the movement inside the case. During a dive, this filled with water entering through minuscule drill holes in a crown and, with increasing pressure, was pushed further, transmitting the ambient pressure via a lever mechanism to a flyback hand. On the dial, a white central hand showed current dive depth to a maximum of 45 metres, while an additional flyback hand, likewise designed as a central hand, remained stationary at the greatest depth attained. However, since the axes of the gauge's indicators went straight through the middle of the movement, there was no room left for a large seconds hand. Divers prefer to have a seconds hand because it is useful for timing decompression stops but also provides reassurance that everything is functioning as it ought to. This was the reason why, 10 years later, in the Aquatimer Deep Two, the depth indicator ran around the movement. Only the bent-over tips of the two indicators, which protruded from a semicircular slit in the dial, moved across the calibrated scale to the side. It was a smart solution that did away with the need for the axes to pass through the movement and made room for a seconds hand.

In both the Aquatimer Deep Two and the new Aquatimer Deep Three, the pressure-metering system is housed in a large second crown on the left-hand side of the case, protected by a bow. Water pressure acts directly on a membrane in the crown and pushes a pin towards the interior of the case. This movement operates the lever system that integrates the two indicators. During a dive, the blue depth indicator moves with increasing or decreasing depth across the white scale and always shows current depth. With the help of the seconds hand and the depth gauge, it is possible to keep ascent speed to a maximum of 10 metres per minute. The red indicator remains at the deepest point attained during the dive, to a maximum of 50 metres. This figure is vital for calculating any necessary decompression stops and, together with the other data, gives the experienced diver all the information he needs to complete the dive safely. The continuous improvement of the rotating bezel system and depth gauge over three generations of the watch nicely illustrates what is probably Charles Darwin's best- known quotation: "It is not the best of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change."

Lighter
Thanks to its titanium case, the Aquatimer Deep Three is lighter than its predecessor in stainless steel. The watch appears less bulky because of the slimmer rotating bezel with its rounded recessed grips. This is despite the watch's diameter, which at 46 millimetres remains unchanged, and the addition of two new functional elements on the right-hand side. The reset button for the maximum depth indicator has moved from "8 o'clock" to "2 o'clock". The push-button made of ceramic is used to reset the maximum depth display to zero. The titanium cover at "4 o'clock" conceals the sliding clutch mechanism for the new rotating bezel system.

Despite the many displays, the black dial remains simple and uncluttered. The Super-LumiNova® coating guarantees excellent legibility no matter how poor the visibility. In addition, the use of twin colours makes it easier for divers to keep their bearings in the dark. The displays relevant to the dive itself, such as depth, dive time and the minute and seconds displays are green, while the hour hand and indices are blue. The reliable 30120-calibre automatic movement with date display comes with a 42-hour power reserve. The back of the watch, secured with five screws, features an intricate relief engraving of a diver's helmet, symbolizing the Deep Three's suitability as a professional diving instrument. The corrugated rubber strap stretches and adjusts itself flexibly to fluctuations in the girth of the wrist experienced when diving or with changing temperatures.