Longines

• cal. 21.29 manual winding nickel-finished jewelled lever movement • two-tone silvered dial with three coloured circles with related hands, fan-form power reserve at 6 • aluminium case protected from vibration by five springs and screwed into a wooden glazed box • dial, case and movement signed

Please note that the movement has not been checked for timekeeping accuracy and Sotheby's will not be held responsible for any repairs should they be require. Movement is in working order while cataloguing and the double split chronograph function appears operational. Dial in good condition with an oxidation mark between 7 and 8. Case in good overall condition but with scuffs and scratches. The mahogany box in good condition with wear to the edges. Overall in good condition.
"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.

Important Notice regarding importation into the United States of Rolex watches
Sotheby's cannot arrange for the delivery of Rolex watches to the United States because U.S. laws restricts the import of Rolex watches. The buyer or a designated agent may collect the property in the country of sale."

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.