The Reverso Chronographe retrograde in pink gold. The genesis of the project and technical analysis. In 1991, Jaeger-LeCoultre launched a new production chapter to celebrate the 60th anniversary of the Reverso, the watch that has become a legend in the world of wristwatches. Starting in that year, the "Reverso Limited Series in pink gold" collection was progressively created over the course of a decade, based on the new Grande Taille case, slightly larger than the Classic case in use at the time, and suitable for complicated movements; this series enabled the Maison's technicians to create precious shaped movements and to produce specimens that were surprising in terms of their complexity, using the two sides of the case as the same number of dials (1). The first watch in the series was, in 1991, the Reverso del 60°, made in pink gold and in a limited series of 500 pieces, which was powered by Jaeger-LeCoultre's hand-wound Calibre 824 with bridges and plates in 14-carat pink gold. This was followed by five other timepieces, all produced in a limited series of 500 pieces with the same case in pink gold only: the Reverso Tourbillon of 1993 (calibre 828), the Reverso Répétition Minutes of the following year (calibre 943), the Reverso Chronographe Rétrograde of 1996 (calibre 829), the Reverso Géographique of 1998 (calibre 858) and finally the Quantiem Perpetuel of 2000 (calibre 855). Each complication was considered separately. The team of master watchmakers, engineers, designers could concentrate on that single complication, distinctive of a specific model, considering all the aspects and elements underlying the production programme. The six Reverso limited series in pink gold encapsulated all the talents who worked within the Manufacture as master watchmakers (2). In any case, although there were individual watchmakers at the helm of a given watch project, as responsible, the entire production of the rose gold Reverso series was a collective effort in which everyone was involved to learn how to build, improve, complete (3). Pink gold watches had to be hand-wound to emphasise the close relationship between the mechanical watch, which required winding every day, and the wearer, as a distinguishing element between mechanical watches and quartz watches, which did not need winding (3). Manel Guerin is remembered as the person responsible for the design of the retrograde Reverso Chronographe (2). From a technical point of view, the case of the 1996 Chronographe is also in the GT format, with a height of 36 mm and a width of 26 mm, with a thickness of 9.5 mm; including the lugs and the support, the height reaches 42 mm. Since the lug extensions are stubby and quite wide, the visual area of the watch is about 350 square millimetres, equivalent to that of a round diameter of a 37.5 mm watch. The programme for a chronograph calibre for the rectangular case of the Reverso (calibre 829) began towards the end of 1992. The project was completed in just over three years at Jaeger-LeCoultre, and twenty prototypes were built (the first ones had two circular subdials on the "back": the seconds counter and the 60-minute timer) and a "zero series" of twenty watches, which were distributed to retailers, but only used for promotional purposes, for example at trade fairs and exhibitions around the world (4). The hand-wound 829 chronograph calibre was designed entirely from scratch, including the time base, on the basis of the automatic 960 calibre used in the Master Lady. The creation of a new time base, different from that of the 822 calibre of the Reverso Gran Taille, was necessary to align the winding crown with the chronograph push-buttons on the case middle, since with the 822 calibre the crown would have been lower than the push-buttons (4). Three years of study and testing were needed for the designers to create a series of solutions tailored to the very particular architecture of the Reverso Chronographe Retrograde and to miniaturise each of the 317 components of the movement to fit into a volume initially intended to accommodate fewer than 200 (5). Philippe Vandel once described its development process as the most gruelling and even more arduous than that of the 1993 tourbillon (6). Jaeger-LeCoultre reportedly took years to perfect this movement, with shipments delayed to buyers (7). In the history of watchmaking, it is very rare for a shaped chronograph movement to be produced. Rectangular watches with a chronograph function were almost all equipped with round movements and had only a rectangular or square case and dial. The designers of the JLC were forced to redesign all the levers and bascules and move them to different positions than usual. In a space of 17.2 mm x 22.6 mm, the designers of the JLC movement developed 317 parts, including a column wheel and retrograde chronograph minute hand. If one converts this shape calibre into a round movement the dimensions would be equivalent to a 10"' line calibre (22.5 mm diameter), with a thickness of only 4.5 mm, with 28,800 Alt/h and a power reserve of 44 hours. The total weight was 79 g. The complexity of the movement also required the use of a double dial: the first is the classic one, in guilloché solid silver, showing the hours, minutes and date, and indicating whether the chronograph was running or stopped; the second was reserved for reading the chronograph functions, with the retrograde seconds and minutes counters perfectly integrated into the bridges, the column wheel, and the other chronograph elements, all visible through the sapphire back (5). Placing the chronograph seconds and minutes on the back of the watch meant that part of the traditional technique used to make a chronograph also had to be modified. In fact, while in other chronograph calibres the chronograph conductor wheel is mounted on the same axis as the continuous seconds wheel, in solidarity with the latter, in this case it is placed in series in order to invert the motion of the wheel itself to the central chronograph wheel, which, being in the opposite quadrant to the hours and minutes, must have its motion inverted in order to see it rotate clockwise (4, 8). The other technical innovation was the retrograde system for the chronograph minutes. First of all, the minute wheel is not driven, as in classic chronographs, by a finger placed under the central chronograph wheel and a return wheel driven by the aforementioned tooth, but by a pinion which constantly meshes with the return wheel, which, equipped with a pinion, is connected to the chronograph minute wheel. The latter therefore receives a uniformly progressive movement: the chronograph minute wheel was therefore continuous (4, 8). But the motion of this wheel is transmitted to the chronograph minute hand, which is located at the bottom of the movement by an ingenious system. A snail-shaped cam is mounted on the minute hand wheel, on which a long lever rests and crawls, and which rests on the tail of a sector of the wheel. The latter meshes with a pinion on which is mounted the minute hand, which rotates on a dial 180° wide. The same pinion meshes in turn with another sector of the wheel on which a spiral spring is mounted; the latter is wound while the hand moves from 0 to 30 minutes. When the hand reaches the 30th minute, the beak of the lever which rests on the spiral cam, having reached the apex furthest from the centre of the cam, falls into the part closest to the centre itself. This abrupt movement, in the opposite direction to the slow, progressive movement which had taken place previously, causes the pressure on the tail of the first wheel sector to suddenly stop. Consequently, the spiral spring of the second wheel sector acts on the latter, animating it with a contrary motion to before and consequently causes the pinion on which the chronograph minute hand is mounted to rotate, causing it to return instantaneously to zero (4, 8). Finally, the last technical peculiarity of the watch is the trapezoidal indicator on the hours and minutes dial, which indicates the start or stop status of the chronograph function; this indicator has an axis which runs through the whole movement and is moved by the column wheel by means of a cam which is rotated clockwise by the column wheel itself when the chronograph starts, and anticlockwise by a spring when the chronograph stops (4, 8). Today, the Reverso Chronographe Retrograde is still one of the most appreciated models in the "Reverso Limited Series in pink gold" collection, which, due to its originality and prestige, can be considered truly unique in the field of watchmaking (9). Biblio-webgrafia 1) Reverso, the living legend, M. Fritz, 1992, Braus ed. 2) The Jaeger-LeCoultre Manufacture Book, 2002-2003 3) https://www.watchprozine.com/jaeger-lecoul...erso/5873708/2/ 4) L'Orologio, La Macchina del Tempo, n° 41, January 1993, Argò s.r.l ed. 5) The Collections - The most prestigious mechanical watches in the world n° 8, Tourbillon ed. 6) https://www.watchprosite.com/jaeger-lecoul...268388.1747292/ 7) https://www.watch-wiki.net/index.php?title...R%C3%A9trograde 8) Orologi- Le misure del tempo , n° 105, march 1997, Tecnimedia ed. 9) Il meglio da il Polso Tutti gli orologi da ricordare, volume 4, 1997, Studio Zeta ed. P.S. I Apologise for my English. I hope you enjoy my research. Any observation is welcome. Translated with www.DeepL.com/Translator (free version)
Good information. I actually had one of those chronographes when they first came out, and I sold it about 12 years ago, something I've regretted since. They were really a complex, complicated movement.