Swiss, Case No. 1405 4635, 54 mm, 108 g, circa 1795
A gentleman's very fine pocket watch with calendar and equation of time Case: 18k pink gold, polished, case maker's punch mark "ALH". Dial: enamel, eccentric hour indicator with Arabic numerals, central sun hand for equation of time, two subsidiary chapter rings indicating date and month with the number of days, gold hands. Movm.: full plate movement, keywind, firegilt, chain/fusee, virgule escapement, three-arm brass balance, fine florally engraved and pierced balance bridge.
The equation of time describes the discrepancy between two kinds of solar time. These are apparent solar time, which directly tracks the motion of the sun, and mean solar time, which tracks a fictitious "mean" sun with noons 24 hours apart. Apparent (or true) solar time can be obtained by measurement of the current position (hour angle) of the Sun, or indicated (with limited accuracy) by a sundial. Mean solar time, for the same place, would be the time indicated by a steady clock set so that over the year its differences from apparent solar time average to zero. Source: http://en.wikipedia.org/wiki/Equation_of_time, as of 02/13/2015.
Diagram of the equation of time. The circle represents the fictitious orbit of Earth and the "kidney" shows its actual orbit around the sun (according to Prof. Herbert Dittrich, "Die Messung des Augenblicks", 2008).
Estimate 16,500 - 18,500 €
Price Realised 21,700 €
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