Unusual French Montre Simple cylinder watch with date Circa 1818

Gold pocket watch with short chain by Breguet et Fils
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A fine and unusual Swiss gold ruby cylinder watch, Montre Simple, with date and short chain, circa 1818. This watch features a gilded movement with a ruby cylinder escapement, a plain three arm brass balance, and a spiral spring with a bimetallic compensation curb, complemented by parachute suspension. The silver engine turned dial showcases a satin finished chapter ring with Roman numerals, an outer minute ring, two engine turned subsidiary dials with contrasting designs for seconds and date, and blued steel hands. Dial signed Breguet et Fils, with an additional secret signature on either side of 12 o’clock, marked as Breguet No. 2348.
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The pink gold case includes an engine turned back with a small central cartouche monogrammed with an A beneath a coronet. It features an engine turned band and bezel, a gold pendant and bow, and a gilt metal hinged cuvette with a winding aperture signed Breguet No. 2348. The inside case back is numbered B 2348, additionally marked 167[?], and bears Paris control marks from 1804-1819, along with the case maker’s mark AG beneath a star for Amy Gros. It comes with a short gold chain and is accompanied by a Breguet certificate dated January 28, 2020.
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This watch was sold to His Royal Highness the Duke of Cambridge on 10 April 1818 for 1,172 francs.
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Diameter: 56 mm
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Signed: Breguet et Fils
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The movement is operational but would benefit from a service and overhaul. There are a few light scuffs and scratches on the plates, but overall, it is in good aesthetic condition. The dial shows some tarnishing, particularly from 11 to 1 o’clock and from 5 to 7 o’clock. There is a small scratch to the left of the subsidiary seconds chapter ring, extending into the hour chapter ring at 8 o’clock, along with some other minor marks and scuffs. The engine turning on the case generally remains clear, although the bezel shows signs of wear with a loss of definition, and there is slight rubbing towards the edges of the case back. The lozenge shaped cartouche within the case back is marked “AG” beneath a star. Included is a non matching silver and gold mounted double ended female ratchet key with a sliding adjusting pin, which does not fit the watch.
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Prince Adolphus, Duke of Cambridge (1774-1850), was the youngest son of King George III to survive childhood. 
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The current watch features one of Breguet’s renowned innovations: the pare-chute suspension. While crafting his timepieces, Breguet noticed that the pivots in the balance wheel were highly delicate and at risk of breaking if the watch was dropped or subjected to physical impact. In 1790, he embarked on developing a shock protection system to prevent such damage. He designed the pivots in a cone shape, secured by smaller cone shaped dishes, and mounted on a strip spring. This design allowed the robust pivot shoulders of the balance staff to absorb shocks, significantly enhancing the watch’s durability.
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In a famous demonstration of this shock absorption system, Breguet attended a gathering at the home of his friend, the French Minister of Foreign Affairs, Charles Maurice de Talleyrand. He dramatically threw his watch to the ground and invited a guest to inspect it, proving it remained undamaged and fully functional. By 1806, Breguet had perfected the design and incorporated it into many of his watches. This innovation paved the way for the Incabloc and other modern shock absorption systems. Also known as the suspension élastique.