A gentleman’s Hour Angle watch, by Longines, the signed silvered and gilt dial with black Roman numerals and 0-180 degrees scale, with inner mobile dial with 0-60 seconds and 0-15 degrees scales, the rotating gilt bezel marked for 0-16, with 15 second divisions between, the signed jewelled automatic movement numbered ‘L989.2’, under glass, the stainless steel case with hinged back cover signed and numbered ‘989.5215’ and ‘24542123’, to black leather strap, cased and with accompanying papers, dial diameter 30mm. £800-£1,200

The original Longines Hour Angle Watch was historic timepiece, designed by the pioneering pilot Col. Charles A. Lindbergh in 1930. The watch was designed to work with the Weems System of avigation to allow easy calculation of the Hour Angle (equivalent to Longitude). Prior to this Lindbergh had had to navigate his flights using ‘dead reckoning’.

In 1987 to celebrate the 60th anniversary of the aviators historic solo flight from New York to Paris, Longines issued this 4/5th size replica of Lingbergh’s original wristwatch, which is now on display in the National Air and Space Museum of the Smithsonian Institution in Washington.

The dial of the watch simultaneously shows time (hours, minutes and seconds) and longitude (degrees and minutes of arc). The mobile inner dial shows the seconds and can be rotated by means of the crown for synchronisation with the radio time signal, while the mobile bezel permits correction for the equation of time, which varies from day to day.