Lindbergh Hour-Angle Longines

Lindbergh Hour-Angle Longines, "Lindbergh", No. 5575398, case No. 2077028. Made in the 1930s. Fine, very rare and unusual, large "hour-angle" centerseconds, stainless steel "Staybrite" aviator's wristwatch. Four-body, polished, revolving bezel with blue and black enameled 15 degrees graduation, graduated band, the ballshaped crown also activates the revolving central dial, hinged back. Hinged "Staybrite" cuvette. White enamel with painted radial Roman numerals for the 12-hour indication, the 180 degrees in blue Arabic numerals, central revolving matte silver dial with painted black radial Arabic numerals for the 60 minutes and painted red radial Arabic numerals for the 15 degrees. Blued steel Breguet hands. Cal. 18.69N, frosted gilt, 15 jewels, straight-line lever escapement, monometallic balance, blued steel Breguet balance-spring, micrometer regulator. Dial, case and movement signed. Diam. 48 mm. Thickness 15 mm. From “The Collection” Notes The hour angle system was invented by Philippe Vanhorn Weems of the Annapolis Naval Academy, who trained Charles A. Lindbergh. The large ball-shaped winding-crown enables the watch to be wound by a pilot wearing gloves. It is practically impossible to build a commercial timepiece which will keep time to the exact second in a ship or an airplane. The inevitable variation from true time necessitated an extra calculation in navigation to compensate for this chronometer error. Weems felt that in an airplane, taking time to ca