Jumping Hour

Early horologists must have wondered about the best way to display the passing of time. Surprisingly, they began by using sound, so that everyone living in towns and villages could know the time simultaneously. This is no doubt why the French word clocher (belltower) and the English term “clock”  both derive from the Late Latin word clocca (bell). However, this system involving a bell struck with a hammer to indicate the time soon reached its limits, as one had to wait for the hour to chime to know the time. Blacksmith-clockmakers therefore invented a dial with hands, inspired by a shadow across a sundial.

Apertures first appeared in clockmaking during the Renaissance. The French term guichet literally means a small window. In everyday language, it refers to a small opening, sometimes fitted with a grid, cut into a door or wall to enable communication while keeping two people physically separate – such as in a castle, a prison or a bank. The opening must be large enough to enable interaction, yet small enough to limit contact to what is strictly necessary.

In horology, guichets were not initially used to indicate the time. One of the oldest and most remarkable examples can still be seen in Prague today, where around two million tourists annually admire the astronomical Orloj, its mechanical heart beating for over 600 years.

Above the dial, two small openings in the tower’s façade reveal an hourly procession of the twelve Biblical apostles. While these are actual windows, they foreshadow watch apertures.

The first apertures were used to display information supplementary to the time itself, generally of an astronomical nature. They can be found on 16th-century table clocks to indicate moon phases, and later, in the 17th century, to show the month or day of the week. Nevertheless, even on watches with astronomical complications, watchmakers long favoured the use of hands and aperture-type displays remained the exception. They only truly became established in wristwatches with the introduction of date windows at 3 o’clock.  

The display aperture leaves just enough space to read the necessary information, be it the date or time, but nothing more. For these indications to remain legible, they must be held in place for as long as required before jumping to the next hour or date at the appropriate moment.

In watchmaking, displays can advance in three different ways. The first and by far the most common is known as “trailing”: the hands advance with each movement of the escapement, i.e. six to eight times per second. The more complex second system is called “semi-instantaneous”:  it remains stationary for a set period and then advances to the next time or date in a matter of seconds or minutes. The third system is the most sophisticated, the most delicate and consequently the rarest. The display remains perfectly still for the necessary period, while the mechanism gradually accumulates energy which it then releases all at once when the time comes, causing the display to “jump” to the next figure. This is the “jumping” or “instantaneous” system. It is found in deadbeat seconds watches, calendars – and quite logically in “jumping-hour” watches.

The energy released to make the hour jump forwards is colossal – on a horological scale of course. This display poses several technical challenges, notably including the risk of the system jumping two units at once, as well as the difficulty of adjusting the time in both directions. Entitled “Jumping Hour Watches”, one of the few technical articles dedicated to this subject was published in 1932–33 in The Horological Journal. The curious reader will discover therein the snail-shaped cams, star-shaped wheels, levers and other springs driving the jumping hour, a few examples of which are reproduced here. 

Calibre 7122 powering the Neo Frame watch presented in 2026 (Chapter 11) combines two concentric discs. The smaller trailing disc indicates the minutes, while the larger jumping disc shows the hours. It is driven by a four-star spring that completes one revolution in four hours to wind a lever that releases its energy every 60 minutes, driving the hours disc. A patented system prevents a double jump. To keep the mechanism suitably thin, the time can only be set by turning the hands clockwise.  

For centuries, jumping-hour displays remained the exclusive  preserve of pocket watches. In July 1915, Swiss watchmakers Alfred Spori and Arthur Dubois filed patent CH71942, which was reviewed the following year by the Revue Internationale d’Horlogerie, for what would likely become the very first jumping-hour wristwatch. Dutch collector and researcher Ruud Van Rijd discovered one of the extremely rare examples ever made: proof that the patent did not remain without effect. Nevertheless, the extreme scarcity of these watches suggests that the war put an end to the project.

It was not until 1924 that the story really began. Audemars Piguet then introduced what is, until proven otherwise, the second jumping-hour wristwatch ever produced. Sold to Gübelin in June 1924, the first example corresponds to Pre-Model 176. It was fitted with Calibre 10HPVM, which was replaced by Calibre 10GHSM as of the third watch delivered (December 1924). Specially developed for the occasion, it revealed its properties via its designation: G for Geneva quality, HS for Heure sautante  (jumping hour) and M for mince (slim).

Produced from 1924 and sold until 1951, Calibre 10GHSM (LeCoultre movement blank) was fitted in just under 600 watches, of which 347 featured a jumping-hour display. Subsequently, this calibre was used in simple hours-and-minutes watches, as well as in 108 calendar wristwatches (see Audemars Piguet 20th Century Complicated Watches, pp. 85-113).

The archives list 212 watches combining an hours aperture and a minutes hand, sold between 1924 and 1951 (95% of them before 1935). The cases could be square, cushion-shaped or rectangular (often referred to in the archives as “tortoise rectangles”). A few rare examples feature hinged lugs, known at the time as “movable lugs”.

From the mid-1920s to the mid-1930s, the jumping-hour trend spread throughout the Swiss watch industry. Numerous manufacturers competed to demonstrate their  creativity, including Haas Neveux & Cie, Cartier, Juvenia, Helvetia, Patek Philippe, Robert Cart and C. H. Meylan.

The defining feature of the Streamline style is aerodynamics. Closely related to the Art Deco movement, it flourished during the interwar period, particularly in the United States. In its quest for modernity and speed, society was then fascinated by aviation, automobiles and high-speed trains. While the Pennsylvania Railroad Class S1 locomotive – nicknamed “the Big Engine” and designed by design pioneer Raymond Loewy – was built to whizz through the air at high speed, its aerodynamic curves could also be found on other objects such as lamps, irons, toasters and certain watches.

Produced in a run of 14 between 1929 and 1930, Pre-Model 1271 is perhaps the most Streamline watch of its time. Its two-part metal case seems designed for speed. The lateral gadroons glide along the edges of the case, curving and tapering until they meet at the tips of the lugs, like an aircraft wing with a stream of ultra-fast air flowing over it. The apertures are reminiscent of the portholes and cockpit window of a Douglas DC-3. Inside,  two small glass plates, each a quarter of a millimetre thick, are held in place by tiny springs. Despite the No. 339 hallmark depicting a headless hammer, the identity of the case maker remains unknown.

Like the Streamline style, watch no. 40546 has a resolutely American history. Its case is engraved with the inscription “Maurice Miller, 1552 Broadway, NYC”. In 1930, Maurice Miller had just taken over the company founded by his father Israel Miller, the king of footwear for music hall performers. The address on the watch corresponds to the I. Miller building, a true temple to footwear built in 1926 just a stone’s throw from Times Square. Until its demise in the 1970s, the I. Miller brand was a major player in the US footwear industry and Andy Warhol himself created advertisements for the brand in 1955.

For now, back to Model 40546. The sole platinum version of the 1271 Pre-Model, it was delivered to the Swiss retailer Beyer on 20 March 1930 for the price of CHF 500. Acquired in 2016 by the Audemars Piguet Heritage Foundation, it is currently on display at the Musée Atelier in Le Brassus. It was this watch that inspired the Neo Frame collection of which the first model was introduced in 2026 (Chapter 11).

In 2016, Audemars Piguet’s CEO François-Henri Bennahmias brought together a small team from the Product and Heritage departments to ask them a question: “Which vintage watches would you dream of seeing revived in the 21st century?”. The project was named “Millésimes”. Around 20 watches were shortlisted and two of them would go on to serve as the basis for the first [RE]Master limited editions, released in 2020 and 2024. The third was the Streamline 1271 Pre-Model, customised for Maurice Miller (Chapter 9).

In October 2025, as this third project was nearing completion, Ilaria Resta, who had taken over as CEO in 2024, decided  to give it a broader destiny than the [RE]Master series and make it a collection in its own right. Model 15245 was unveiled in February 2026 to the press and a select group of clients at an event in Andermatt, in the heart of the Swiss Alps. The reception was highly enthusiastic, and the watch was perceived both as a tribute to the 1920s and to the Space Age style.

Powered by Calibre 7122, the Neo Frame Jumping Hour (15245) is the first Audemars Piguet watch to offer a selfwinding jumping-hour mechanism. In the 1920s, the crystal was concealed within the case because it was so fragile. Today, a large sapphire crystal is secured to the case cover. Almost as hard as diamond, it is now the crystal that protects the metal. While water resistance is usually achieved by press-fitting the crystal onto the bezel, the Neo Frame Jumping Hour model features neither a bezel nor metal at 12 and 6 o’clock, leaving the sapphire crystal exposed. To achieve water resistance to 20 metres, the dial plate is bonded to the sapphire crystal and then screwed onto the case middle, a new process specially developed for this model.

A variation was unveiled at Watches and Wonders in Geneva (14-20 April 2026). The case was redesigned so that the upper part of the watch is entirely hand-engraved. A tribute to Art Deco, the decoration evokes the New York skyscrapers of the 1920s.

The Neo Frame marks the dawn of a new era of creativity for the independent watchmaker from Le Brassus – as well as the grand return of jumping-hour watches.