French enamel verge watch repeater “à toc et à tact” Circa 1760

Very fine watch with a rare blocking device
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A complicated very fine enamel verge watch repeater “a toc et a tact” with a rare blocking slider for accidental release of the repeater, made by Berthoud in Paris, France, circa 1760. The open faced case of exceptional quality is crafted from 18 Carat gold, worked in three different gold colours, has a five part lateral hinge, back blue and white enamelled, in the case band slider for striking on bell and muting. The original white enamel dial has an outer ring with black Arabic (outside) and Roman (inside) numerals for, respectively, the minutes and the hours, an original hour hand in pink gold, a replaced but from the same time minute hand. The movement has a verge escapement and a repeater for the hours and quarters.
Dial and movement signed
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Diameter: 40 mm
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Weight: 58 g
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Signed: Berthoud, a Paris  
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Ferdinand Berthoud

Ferdinand Berthoud was born in 1727 and died in 1807. He was a Swiss watchmaker and scientist. In 1753 Berthoud was awarded the title of Master watchmaker in Paris. He succeeded in the pioneering work of Henry Sully. At the king’s insistence, he travelled to England to view the chronometers of John Harrison. Ferdinand Berthoud settled in Paris on April 16^th, 1745 at the age of 18, a move that enabled him to perfect his knowledge of the watch and clock-making profession. He rapidly acquired a reputation for technical competence and achieved recognition for his innovations in his field. On December 13th, 1760, Berthoud submitted to the French Royal Academy of Science a Mémoire sur les Principes de construction d’une Horloge de Marine, the famous Marine Chronometer No. 1, whose construction was completed at the start of 1761. In 1770 he was appointed Horloger du Roi (Horologist-Mechanic by appointment to the King and the Navy). Berthoud was also named a member of the Institute right from the time of its creation in 1795. He in the meanwhile became a member of the Royal Society on February 16th, 1764. He is regarded as one of the inventors of the marine chronometer that served to determine the longitude at sea necessary for navigation.
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Montre à toc
Montre á toc is a ‘dumb’ repeater watch in which a hammer strikes the inside of the case to produce a muffled sound. Invented by Julian Le Roy in 1740.
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À tact watch
1. Repeater watch in which hammer and bell are replaced by a sharp pin which protrudes from the case to prick the finger once for each hour.
2. A type of watch made after 1795 by Abraham Louis Breguet to give time by touch. In the late eighteenth century, it was considered impolite to consult one’s watch in company, a question of etiquette which the à tact watch helped to solve (the French tact, meaning touch, has given the English tact and tactful). Knobs representing the hours are positioned around the case with a large hand that could be turned until it meets resistance. Its position in relation to the knobs gave the time. This kind of tactile watch is now mainly used by the blind and visually impaired.