GOLD BREGUET TOURBILLON N. 4342, SOLD IN 1990 Three body circular 18K gold case, n. 4342 A, reeded band, rounded bezel, straight lugs with gold screwed bar, transparent back case. Breguet leather strap and 18K gold buckle.
Silvered dial with guillochè finishing, secret signature between XI-XII and XII-I, brushed hour ring with Roman numerals, tourbillon regulator whose revolution is showed on a sector graduated by 20 units and indicated by a three arms hand. Blued Breguet hands.
Manual winding movement signed “Tourbillon Breguet”, caliber 558, N. 23, gilded and hand engraved, 21 jewels, inscribed "Brevet du 7 Messidor An 9”, 21 jewels, lateral-lever escapement, monometallic balance with screws adjusted to six positions, self-compensating Breguet balance spring, polished steel one-minute tourbillon cage.
Accompanied by Breguet cover box, box and warranty.
Diameter Ø: 36 mm
Note: working. 

The tourbillon regulator is one of the most famous inventions of Abraham-Louis Breguet. Developed with the purpose to compensate the variations in timing adjustment with each change of position of the watch, the tourbillon’s concept consists of installing the balance, the hairspring, the lever and the escapement-wheel inside a mobile cage so that all the flaws, which are regularly repeated, are engaged in a process of mutual compensation.
The Breguet patent dates back to 1801, while the first models saw light a few years later with the first watch available on the market in 1805 and subsequently presented at the National Exhibition of Industrial Products in Paris.
Despite the technical progress of modern watchmaking, the tourbillon has maintained its charm in the eyes of collectors, and it represents Breguet’s aesthetics par excellence.