Important Collectors’ Wristwatches, P...

Geneva, Nov 16, 2008

LOT 449

Breguet, No. 4107. Made in September 1938, sold to the French Aéronautique on December 30, 1938, for 15,800 francs. Fine and rare keyless ?Sidéromètre Breguet Type 101? splitseconds chronograph, Breveté S.G.D.G., froma series of 25 pieces.

CHF 5,000 - 7,000

USD 4,600 - 6,500 / EUR 3,100 - 4,500

Sold: CHF 4,800

C. Painted aluminum box, lined with felt insulation. Three fixing brackets are riveted to the outside. There is no case, the movement being fixed to the underside of the dial-plate, the latter engraved with operating indications. D. White painted with outer seconds divisions and three apertures for the digital degree indications. Blued steel counterpoised hand. M. 24''', high quality, blank by V. Piguet, 21 jewels, two differential winding, one for the going train, the other for the motion works so that the going train can advance the numbered discs with minimal resistance, motion work is very complex and carefully made, straight-line lever escapement, brass-invar "Intégral" Guillaume balance, blued steel balance spring with terminal curve. Signed on the dial, the front plate and on the reverse of the bezel. Dim. 100 x 143 x 118 mm.


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Grading System
Grade: AA

Very good
Case: 4-9

Fair

Scratched
Movement: 3*

Good

Overhaul recommended, at buyer's expense
Dial: 4-6-12-01

Fair

Slightly oxidized

Worn

HANDS Original

Notes

The Sidéromètre, designed in the late 1930s, runs at sidereal, rather than mean time, then converts this into degrees, minutes and seconds of Earth?s rotation. The center-seconds hand rotates in the time the Earth rotates through 1° in relation to the stars. The Earth?s angular rotation is recorded by the numbered discs appearing in the dial apertures: degrees are shown on the right side, tens of degrees in the center, and hundreds of degrees on the left. Since the temperature in an airplane of the period could drop very low at high altitudes, it was necessary to prevent rapid cooling of the inside of the box, which might cause condensation in the mechanism. Though accurately compensated, the watch would have been subject to a transient response due to rapid and extreme temperature change, and this had to be prevented.