About this watch

Reference 116758SARU puts the sapphire and ruby bezel into 18 ct yellow gold, and warm metal changes what the stones do. Against white gold the rubies read as a colour; against yellow gold they read as heat. This one still wears its factory stickers. The difficulty in a bezel like this is not the stones, it is the calibration. Every baguette has to be cut to a size that lets it sit flush against its neighbours around a curve, with no gap and no step, and the colour has to break cleanly from blue to red at the two points where the day half meets the night half. Cut them individually and the ring will not close; cut them to a common specification and the colour match has to hold across two different species of stone. That is the work, and it is why these are set at the factory and not afterwards. The diamonds continue down the lugs and along the case flanks, so the gold is broken up at every edge and the watch reads smaller than forty millimetres from above. The dial keeps the green GMT-Master II text that marks the gem-set references. Calibre 3186 drives it, self-winding, with the local hour hand that jumps in one-hour steps independently of the 24-hour hand. The case is 40 mm in 18…