Paris

The French Wikipedia says the Quai de l’Horloge, built from 1580 with the Pont-Neuf, takes its name from the clock of the Palais de la Cité’s tower.¹

Watchmakers, opticians and instrument makers clustered there: Lépine in 1778-79, Breguet at no. 39 from 1775, the opticians Chevalier at no. 31; Julien Le Roy worked nearby in the Rue de Harlay.^1, 2, 5

Wikipedia records that Breguet’s firm moved from the quai to the Place de la Bourse and later the Rue de la Paix.⁷

The French Wikipedia records that under the Second Empire the small houses and shops along the quay gave way to the Cour de cassation, begun in 1861 on a new line of the quay.¹

The guild controlled who could become a master; Julien Le Roy was one of its jurés, and Berthoud needed a royal council decision in 1753 to be made master outside its rules.^5, 8

Royal patronage gave titles, lodgings and pensions: clockmaker to the King, clockmaker to the Navy, lodgings at the Louvre (Berthoud, and Janvier from 1793).^8, 9, 10

The Académie royale des sciences examined and approved inventions and judged disputes over priority, as between Caron and Lepaute.^2, 8, 11

The history site Hérodote dates to 2 March 1791 the decree that abolished the guilds; from 1 April anyone could practise a trade.¹²

Paris was the seat of the scientific institutions that used precision timekeepers: the Observatory, the Bureau des Longitudes (1795) and the Institut.^3, 13

Many of the leading makers came from outside France or from its borders: Berthoud and Breguet from the Principality of Neuchâtel, Lépine from the Pays de Gex, Janvier from the Jura.^{10, 14, 15, 16}

Parisian makers relied on movements made elsewhere: Lépine's ébauches came largely from Ferney near Geneva, and in 1819 three quarters of Japy's clock ébauches from Badevel were sent to Paris.^2, 17