Large Swiss 18 carat gold keyless lever complicated watch Circa 1860

Gold highly complicated repeater attributed to Louis Audemars
–
An extremely fine and exceptionally rare, large Swiss 18 carat gold open faced minute repeating keyless lever pocket watch with triple-date calendar, moon phases, lunar calendar, Réaumur thermometer and continuous sweep centre seconds with stoppable and jumping extra split hand, circa 1860. Retailed by Marcks & Co, Bombay & Poona. Matte gilt movement, 32 jewels, wolf’s tooth winding, a large going barrel, gold wheel train, counterpoised straight-line lever escapement, cut bimetallic compensation balance with gold meantime and temperature adjustment screws, blued steel Breguet balance spring with overcoil and index regulator, repeating on gongs activated by a slide on the band, a Réaumur thermometer bimetallic curb mounted on the dial plate. A hinged gold cuvette. White enamel dial with Roman hours, outer minute divisions and Arabic five-minute numerals, subsidiary dials for the date, days of the week and months, an aperture for the moon phases with a lunar calendar on the edge and Réaumur thermometer sector below, gold spade hands, blued steel date and seconds hands. The polished case with master mark AM, an engine-turned back, correctors in the band, a button in the crown for the stopping and re-join of the split hand. Dial and cuvette signed Marcks & Co Bombay & Poona, case numbered.
–
Diameter 54 mm
–
Signed: Marcks & Co Bombay & Poona
–
This extremely rare and complicated watch can be confidently attributed to Louis Audemars by comparing it to a near-identical watch with the same type of distinctive calibre and the very unusual seconds and split feature which is illustrated in ‘Louis-Benjamin Audemars’ by Hartmut Zantke, 2003, p. 245. The dial design with the Réaumur thermometer is also quite distinctively Louis Audemars, as is the repeating slide with concave depression.

At first glance, this watch appears to have a split-seconds chronograph mechanism, whereas it has a sweep centre seconds hand which cannot be stopped and then an additional hand which can either travel in unison with the seconds hand or be stopped by depressing the button in the crown and then made to rejoin the seconds hand by pressing the button again. This mechanism is found on only a handful of known watches by Louis Audemars and was made before Adolphe Nicole‘s invention in 1862 of the true chronograph with return-to-zero function. The Réaumur scale also known as the ‘octogesimal division’ is a temperature scale in which the freezing and boiling points of water are respectively set to 0 and 80 degrees. The scale is named after René-Antoine Ferchault de Réaumur, who first designed something similar in 1730.