Accompanied by Longines original fitted presentation box.
The hour angle watch was invented by the renowned American aviator Charles A. Lindbergh and introduced to the market in 1932. Lindbergh rose to international fame in 1927 when he became the first person to make a solo, non-stop Trans-Atlantic flight.
As the accuracy of mechanical watches can be affected by conditions aboard ships and airplanes, the hour angle watch provided a means by which this variation could be readily calculated when used in conjunction with radio time signals.
For an illustration of the original drawing and explanation of the mechanism see Longines by Daria Marozzi & Gianluigi Toselli, pp. 75-79.
Similar watches are also illustrated in Ore d'Oro 2 by Jader Barracca, Giampiero Negretti, Franco Nencini, p. 200 and in Armbanduhren - 100 Jahre Entwicklungsgeschichte by Kahlert, Mühe, Brunner, fifth edition, p. 302.