This watch is horologically significant because it is most likely the earliest stem-wound and stem-set watch. Keyless winding goes back a long time. An advertisement in the London Gazette of January 10, 1686, describes a watch by R. Bowen as being wound without a key. In 1712 John Hutchinson made a watch with "a contrivance to wind up this, or any other Movement without an aperture in the case through which anything can pass to foul the movement". In the second part of the eighteenth and in theeginning of the nineteenth centuries there were numerous attempts to solve the problem of keyless winding (Caron, Jaquet-Droz, Leslie, Berollas, Viner). These featured turning bezels, pulling a lever protruding from the case, pumping or pulling a piston in the pendant, etc.In 1820 Thomas Prest of London invented the first stem winding system. But the hand setting was still done in the old-fashioned way - with the key, which was often lost or misplaced. The system allowing for stem winding and setting was developed between 1820 and 1844. The key figures were Breguet, Louis Audemars, and Adrien Philippe. In his "Les Montres sans clefs" Philippe clearly gives credit to Breguet as the first one to apply the system.We know of 25 Breguet watches from the main series, employing stem winding, some of which also feature stem hand setting. Of these, the present lot has the lowest serial number, indicating that it is the oldest. It was sold rather late but this was probably due to its staggering price of 6000 francs. Of the above mentioned 25 pieces, only one other (No. 5008) cost as much; all the others were less expensive. Further supporting the seniority of the present watch is the fact that watches with highr serial numbers incorporate a more advanced winding/setting system in which the setting crown is placed concentrically above the winding one, while in this watch the system is more basic-the idea of joining the two functions had not, as yet, been realized.The watch possesses yet another unusual feature; the experimental construction of the balance, meant to decrease middle temperature error. Its steel lamina are not of uniform thickness, starting thin at the arm, becoming thicker half-way up, and staying thick up to the cut.