Longines

• cal. 21.29 jewelled manual winding lever movement • two-tone silvered dial, inner ring calibrated for 360 degrees, outer ring calibrated for 60 units, three coloured circles with related hands, fan-form sector for power reserve indication • aluminum case, with heating system and light, outer case with hinged front cover • dial and movement signed • with a locking key for the outer case

The movement and chronograph functions are in working condition at the time of cataloguing. The dial is in good condition. The case has some dents and tarnishing throughout. One of the four screws fixing the glass of the front cover is missing. Outer case numbered 1478828. Note that the heating system and the light in the outer case have not been tested and therefore we cannot guarantee the function of those. The watch has not been tested to determine the accuracy of its timekeeping. Please note that Sotheby's does not guarantee the future working of the movement and that a service may be required at the buyer's discretion.
"In response to your inquiry, we are pleased to provide you with a general report of the condition of the property described above. All dimensions in catalogue descriptions are approximate. Condition reports may not specify mechanical replacements or imperfections to the movement, case, dial, pendulum, separate base(s) or dome. Watches in water-resistant cases have been opened to examine movements but no warranties are made that the watches are currently water-resistant. Please note that we do not guarantee the authenticity of any individual component parts, such as wheels, hands, crowns, crystals, screws, bracelets and leather bands, since subsequent repairs and restoration work may have resulted in the replacement of original parts. Since we are not professional conservators or restorers, we urge you to consult with a restorer or conservator of your choice who will be better able to provide a detailed, professional report. Prospective buyers should inspect each lot to satisfy themselves as to condition and must understand that any statement made by Sotheby's is merely a subjective, qualified opinion. Prospective buyers should also refer to any Important Notices regarding this sale, which are printed in the Sale Catalogue. In particular, please note it is the purchaser's responsibility to comply with any applicable import and export matters, particularly in relation to lots incorporating materials from endangered species.NOTWITHSTANDING THIS REPORT OR ANY DISCUSSIONS CONCERNING A LOT, ALL LOTS ARE OFFERED AND SOLD AS IS" IN ACCORDANCE WITH THE CONDITIONS OF BUSINESS PRINTED IN THE SALE CATALOGUE."

**Please be advised that bands made of materials derived from endangered or otherwise protected species (i.e. alligator and crocodile) are not sold with the watches and are for display purposes only. We reserve the right to remove these bands prior to shipping."

Longines developed the Siderograph to satisfy the increasing need for accurate aeronautical night navigation during the 1930s. Existing systems had relied upon radio signals but the Siderograph enabled navigation by the stars, (astronavigation), which had previously been very difficult in a fast-moving vehicle. Using Longines’ most accurate movement, the Siderograph is designed to operate on Greenwich sidereal time with the dial calibrated in hour angles, and minutes and seconds of arc. Used in conjunction with a sextant, and a chronometer set to Greenwich Mean Time, the navigator uses the split-second functions of the Siderograph to set the vernal equinox hour angle and thus pinpoint exact position. The Siderograph became available in 1938 and in the same year the American billionaire, Howard R Hughes flew around the world in 91 hours in an aircraft equipped with Longines instruments which included a Siderograph. 

Information about the Siderograph can be found in: Daria Marozzi and Gianluigi Toselli, Longines, Giada, 1990, pp. 100-107.