Hamilton Khaki Automatic X-Mach

The Hamilton Khaki Automatic X-Mach is an aviator watch. This sophisticated timepiece boasts of the horological ability to measure the Mach number of an aircraft, in simple terms: the speed of an aircraft relative to that of sound.

This timepiece houses an automatic ETA Valjoux Caliber 7750. It contains 28 jewels that vibrate at 28,800 times per hour. The main functions are hours, minutes, subsidiary seconds; chronograph; date and weekday.

The Hamilton Khaki Automatic X-Mach black PVD-coated stainless steel casing has a generous diameter of 44mm. The bezel has a tachymeter scale on it, and the angled flange has a calculating table. Pilots who need to use the Mach function can simply set the pressure altitude (PA) and calibrated air speed (CAS) by turning the left crown of the watch to reveal the Mach number in ISA (International Standard Atmosphere) conditions on the bezel, turning the timepiece into a portable Machmeter.

The crown is screwed in. Water-resistance is to 100 meters. The face and a transparent arrow-head case-back are both made of sapphire crystal and are anti-reflective.

The smooth black dial is teamed with silvered Arabic numerals and indexes with matching subdial. The date display at 3 is uniquely contrasted against a white wedge shape that is reminiscent of the one underneath a stationary plane's wheels, and is adorned with a “Clous-de-Paris” pattern. The strap is leather with carbon inlays, lending an interesting detail.