This Patek Philippe 5164A brings a genuine travel complication to the Aquanaut, Patek's most casual sports watch, and in steel it remains the most sought after way to own one. It runs the self-winding calibre 324 S C FUS, whose Travel Time mechanism tracks a second time zone through a pair of pushers set into the left side of the case, the local date shown at six o'clock. The stainless steel case keeps the rounded octagonal Aquanaut outline at 40.8mm across and 10.7mm thick, the twin pushers giving it a little more presence than the numbers suggest. The dial is black, carrying the embossed grid pattern that defines the line. A practical and hard to find Patek that turns a casual sports watch into a genuine traveller's piece.