Arnold & Son Watch Longitude Titanium Fern Green 1LTAT.F01A.N001U. Longitude Titanium is a sports chic COSC certified chronometer with a 42.5mm titanium case. The dial of Longitude Titanium is vertical satin finished in a continuation of the bracelets finish, which is subtly intersected by the polished edges of its links. With a power reserve display at 12 o’clock and an imposing seconds counter at 6 o clock, Longitude Titanium pays tribute to John Arnolds marine chronometers, his revolutionary vision and his decisive role in calculating longitude at sea.