The Complete History of the Amazing Lemania Chronograph Calibre 2310By Wei Koh
Chuck Yeager, Muhammad Ali, Rocco Siffredi… there are certain individuals that are, to borrow from Bernard Malamud’s The Natural, irrefutably, unassailably and undoubtedly superhumanly gifted: “The best there ever was in the game.” The thing is, many pretenders to the throne only understand this when they are confronted by true greatness, leaving them in the sudden, crushing revelation that, try as they might, in the words of the mighty African-American author James Weldon Johnson, “Young man, young man, your arm’s too short to box with God.”
Such was the lesson imparted to rookie Reggie Miller when he encountered the greatest basketball player of all time, His Airness Michael Jordan. Miller recalls that it was his rookie year with the Indiana Pacers when he found himself playing an exhibition game with the Chicago Bulls. On that team was, of course, Michael Jordan, whom Miller describes as being “three or four years in.” He continues, “Most veterans don’t like playing exhibition games — they want to get to the real thing. I’m a wide-eyed, energetic rookie and Michael is going through the motions. Chuck Person, who is on my team, is like, ‘Can you believe Michael Jordan? The guy everyone’s talking about who’s supposed to walk on water? You’re out there killing him, Reg. You should talk to him.’”
Miller chuckles as he recalls, “So I went up to him and said, ‘Michael, who do you think you are? That’s right, there’s a new kid in town.’” Unfortunately for Miller, that was all the motivation Jordan needed. He says, “He looks at me then starts shaking his head. So at half, I have 10 and he has four points. The second half, he ended up with 44 and I ended up with 12. So he outscored me 40-2. As he’s walking off, he turns to me and says, ‘Be careful, you never talk to Black Jesus like that.’”
The Greatest Chronograph Movement Of All Time
For me, the Lemania 2310 or CH 27 — as was its name while in development by the brilliant Albert Gustave Piguet, the movement maker’s technical director — is the most beautiful, historically significant, and yes… the greatest chronograph movement of all time. And yes, I’ve taken into consideration the sublime Victorin Piguet ébauche movements from the 1920s, the Longines calibre 13.33Z and even the Valjoux 13-130.
There are three things that are particularly extraordinary about the 2310. The first is the great technical leap forward it represented in 1942, when it was first launched. At 27mm in diameter and 6.74mm in height, it was the world’s smallest chronograph movement then, beating both the 13.33Z and 13-130, which were both 13 lignes (29mm), by a considerable margin. (As an aside, if you’ve ever wondered why a Patek reference 130 has its sub-dials pushed all the way to the edge of its 33mm case, it is because of the size of the Valjoux movement within.) Being a smaller-sized movement made the 2310 incredibly adaptable to different case styles and configurations.
The second thing is that, from 1946 to 1968, it was used by Omega as the calibre 321, where it had an unrivalled track record for incredible reliability and performance, culminating in it powering the only watches that passed NASA’s torture test for certification for use in space.
The third: as it was really the only manual-wind, column-wheel, classic chronograph being manufactured in ébauche form in the ’80s, it played a seminal role in the Swiss watch industry’s recovery from the Quartz Crisis, allowing maisons such as Patek Philippe, Breguet, Vacheron Constantin and Roger Dubuis to collectively stage the resurgence of the mechanical chronograph. Two of these brands, Patek Philippe and Breguet, even built split-seconds versions of this movement — a considerable technical undertaking as explained to me by the legendary Philippe Stern.
The thing to understand is that without Omega, the calibre 2310 would never have been born. By the beginning of the 20th century, Omega had become synonymous with the chronograph complication. Indeed, it had launched its first pocket-watch chronograph movement, the 19‴ CHRO, a full century before in 1898. This was followed up by the 18‴ CHRO in 1906 which was also a pocket-watch movement, though it was famously adapted for use in the world’s first wristwatch chronograph. Both the 18‴ and 19‴ CHRO were of the monopusher configuration with stop, start and reset all activated by a single pusher. Omega then created a movement called the 39 CHRO which was made between 1929 and 1940. It was still largely used in pocket watches, but occasionally in wristwatches and in monopusher and bi-pusher configuration. Then, something happened called The Great Depression.
The Workhorse Chronograph
The Great Depression, which began in 1929 and endured for a decade, was the result of artificially inflated stock prices. Everyone rode the stock market’s bull rush throughout the heady, lascivious Jazz Age of the 1920s, forging an eerily accurate precursor to the events that led to the subprime mortgage crisis almost 90 years later. Stock prices boomed even as consumer debt spiralled out of control, unemployment rose and the agricultural sector failed due to droughts. Finally, there was a total global loss of confidence in the stock market, and a financial and economic bloodbath ensued. As you can imagine, the demand for mechanical watches was severely impacted. But it is incredible that with every global crisis — the Great Depression, the Second World War, the Quartz Crisis — the best watch brands reacted with creativity and courage.
Strength in consolidation became a key strategy, and with that, Omega, Tissot and Lemania joined forces between 1930 and 1932 in a new group was called the Société Suisse pour l’Industrie Horlogère (SSIH). Lemania became the exclusive movement supplier for Omega, and by 1936, half a million Lemania movements were in production at any given time.
During this period, two of the first truly modern movements created especially for wristwatch chronographs emerged. The first was the Lemania CH 13-based Omega 28.9 CHRO launched in 1932 that measured 29mm in diameter and was characterized by its beautiful V-shaped bridge. The second was the Lemania CH 15-based 33.3 CHRO that measured 33.3mm in diameter and used a distinct U-shaped bridge that would also appear in the Omega 321. This was launched in 1933. Omega watches with the 33.3 CHRO are much sought after as the calibre represents an important precursor to the 2310 or 321. Note that it is clear both the 28.9 and 33.3 movements were in development before the SSIH consolidation.
What has been the source of some discussion is that the orientation of both these movements is opposite that of the 18‴ and 39 CHRO. Meaning that if you had a 33.3 or 28.9 CHRO-powered watch and looked at it from the front and removed the dial, the balance wheel would appear at six o’clock. In the 18‴ and 39 CHRO watches, it would appear at 12 o’clock. Most people feel that this is because the 33.3 and 28.9 were wristwatch movements while 18‴ and 39 were pocket-watch movements, bt quite honestly, no one really knows.
Interestingly, when Albert Gustave Piguet set to work on the Lemania 2310 or CH 27, he flipped the orientation back so the balance was once again at 12 o’clock. What was the impetus for the creation of this new movement?
First, a new movement was needed for wristwatches which had completely taken over from pocket watches in popularity and had considerably smaller diameters. So Piguet was tasked with creating the smallest movement he could and arrived at the 27mm diameter. Second, Lemania and Omega were focused on the creation of a new workhorse chronograph that would be small and slim, and most importantly, feature a 12-hour totalizer that was essential for the burgeoning activities in both auto racing and aviation. Finally, the 2310 would be one of the first critical projects under the newly consolidated SSIH group. So, on all levels, the Lemania 2310 was really a movement that symbolized the advent of the modern world in the 20th century.
The Two-Counter Version Vs The Three-Counter Version
In 1942, the calibre 2310 or CH 27 was introduced in two versions: the CH 27-17P two-counter version (with seconds and chrono minutes) and CH 27-12P three-counter version (with seconds, chrono minutes and 12-hour totalizer). Adding to the complexity, the movement came in a 17-jewel version, which formed the base of the Omega 321, and also a 21-jewel version with swan-neck regulator known as the Lemania 2320. To put this in perspective, all haute de gamme brands that adopted the movement in the 1980s and 1990s would use the 21-jewel, swan-neck-regulator version 2320 but with two counters, so to be exact, they used the CH 27-17P. Omega used the 17-jewel, three-counter version 2310, or to be precise, the CH 27-12P for their Calibre 321.
The calibre 2310 is truly a thing of beauty. Let’s look at some of its central characteristics.
1. The massive balance wheel beats at 18,000vph, although many brands have increased this vibrational speed to 21,600vph.
2. The column wheel is the command centre of the chronograph. All the best chronographs use column wheels to activate the sequence of start, stop and reset.
3. The intermediate bridge holds down the wheel for the minute counter and the all-important chronograph central seconds wheel. Note that this bridge has been the subject of a great deal of artistic expression for different brands. The Patek Philippe bridge is distinctly V-shaped. The Vacheron Constantin bridge is somewhere between a V and Y shape. The Roger Dubuis bridge is fully Y- or wishbone-shaped. The Omega 321 bridge is U-shaped. The Breguet is somewhere between a U and a Y.
4. The reset hammers for the chronograph wheel and minute counter are one piece.
5. The chronograph coupling lever, seconds wheel (co-axial with the seconds wheel that is driving the continuous seconds indicator) and the intermediate or drive wheel are all placed in a compact arrangement just beside the chronograph second wheel.
6. The Lemania 2310 has a very high level of adjustability, including the depth of engagement for the drive wheel.
One image that has intrigued many movement aficionados is the image of prototype automatic Lemania 2310-based movements. These are dated to 1947, but were never put into production. But it is interesting to see that a full 12 years before the launch of the Zenith El Primero, there were already early experiments into an automatic-winding integrated chronograph.
Omega Speedmaster calibre 321, based on the Lemania 2310 or CH 27-12P, 1957–1968
There is no brand more synonymous with the amazing Lemania 2310 than Omega. In 1946, Omega created its own version of this movement and dubbed it the calibre 321.The Speedmaster chronograph was initially created to meet the demands of a burgeoning auto-racing culture that was sweeping the United States and Europe. While the movement had been used in several Omega models before, it found its true home in a new chronograph with the first-ever tachymetric scale engraved on the bezel — the Speedmaster. Legend, of course, goes that this watch was subsequently certified as the official timepiece for NASA. Every watch that received this certification and that went into space was one of the following three models: the 105.003, the 105.012 and the 145.012. And they all used the calibre 321.
Speedmaster references 105.003, 105.012 & 145.012 were three references certified for manned space missions by NASA; every one of these watches featured a calibre 321
As homage to this movement’s incredible history, Omega’s brilliant CEO Raynald Aeschlimann brought the movement back last year. It is constructed in a purpose-built section of the Omega manufacture. Every movement is assembled, regulated, finished and cased by one individual watchmaker, who then personally signs the warranty card for that 321 watch. Aeschlimann is quick to point out that the modern calibre 321 is not a gussied-up Lemania 2310 ébauche but a ground-up development.
Says Aeschlimann, “When we asked Speedmaster collectors what their dream was, the vast majority said they wanted to see a resurrection of the calibre 321. So we thought if we are going to do this, we have to do it the right way.” Rather than using an existing Lemania 2310 ébauche from their Swatch Group sister brand Breguet, Omega decided to completely and accurately reverse-engineer the original 321 calibre, down to its exact specifications. In order to do this, Omega’s team, helmed by Aeschlimann, had to petition the Swatch Group’s board of directors.
From a purely financial perspective, it made no sense to resurrect the 321, especially not in the way Omega intended, which involved a slice-by-slice 3D tomographic scan of the movement found in astronaut Gene Cernan’s actual ST 105.003 timepiece that he wore to the Moon and that is now found in their museum. The cost of this scan alone was over one million Swiss francs. To replicate the exact pallet with its very specific guard pin, Omega also had to approach Nivarox to recreate this component down to its finest details.
“The only way we could truly respect this incredible movement and all its devotees, as well as the legions of fans passionate about the Speedmaster’s history, is [to] go down to these painstaking details and bring the 321 back in its full integrity and authenticity. That is the only way for us here at Omega,” says Aeschlimann.
Patek Philippe calibre CH 27-70, based on the Lemania 2320 or CH 27-17P, 1985–2011
In the ’80s, the Lemania 2310 became a canvas of expression for watchmaking’s most revered maisons. The first of these was Patek Philippe. Amazingly, Philippe Stern used this movement in 1985 to replace the Valjoux 13-130 of the 2499, creating the amazing 3970 perpetual calendar chronograph. In Patek-speak, the movement is called the CH 27-70. Thanks to the Lemania 2320’s 27mm diameter, he was actually able to make a smaller watch at 36mm in comparison to the 2499’s 37.5mm diameter. The chronograph-only version — the 5070 launched in 1998 — would conversely be the largest Patek chronograph ever serially produced at 42mm. These two watches show the amazing adaptability of this movement for watch designs. The CH 27-70 continued to be used in the successor to the 3970, the larger 40mm-diameter 5970 designed by Thierry Stern, and also in the iconic perpetual calendar with split-seconds function, often considered one of the Holy Grails of watch collecting, known as the Patek Philippe 5004, produced from 1996 to 2011.
Breguet calibre 533.3, based on the Lemania 2320 or CH 27-17P, circa 2000s–present day
The ’70s was a turbulent period in Switzerland with the watch industry reeling from the effects of the Quartz Crisis. At the very bleakest moment, one extraordinary man emerged to save the Swiss watch industry. His name was Nicolas G Hayek.
Hayek had established a reputation as a restructuring expert when he was asked to oversee the liquidation of two groups, Allgemeine Schweizerische Uhrenindustrie AG (ASUAG) and the previously mentioned SSIH. But instead of liquidating them, he realized he could save them if he could make them more efficient. The first thing he did was consolidate them both into one group named the Société de Microélectronique et d’Horlogerie (SMH, later to be renamed the Swatch Group).
When he did his analysis of ASUAG, Hayek was shocked to discover the profound inefficiencies of the 100-plus companies, all of which were doing separate R&D, marketing and assembly. He introduced the concepts of streamlining and verticalization, and in a lesson clearly learned by the German auto industry, invested in the standardization of parts. In this process, he discovered a project on making simple, efficient mechanical watches using 51 parts instead of the usual hundreds of parts, and he named this the Swatch watch, and using dynamic marketing techniques, created the first mass shift against the Quartz Crisis.
Lemania came out of the SSIH group in 1981. It was renamed Nouvelle Lemania and was purchased by Breguet in 1992. Swatch Group purchased Breguet in 1999 and with it, Lemania. The brilliance of Nick Hayek was to always verticalize production. Just as Blancpain has Frédéric Piguet, Breguet had Lemania. To be fair, Lemania would have had much of its production dedicated to its historical ally, Omega, which was also Hayek’s motivation for purchasing Breguet. Amongst the various movements in the Lemania arsenal that were lying dormant like a sleeping giant was, of course, the amazing Lemania 2310/2320. As such, the creation of beautiful Classique-cased chronographs using the venerable Lemania 2320 seemed only natural. The modern version of this watch is the reference 5287.
The Breguet 5287 is a watch for horological purists. It has all of the iconic design language created by Abraham-Louis Breguet. Says Emmanuel Breguet, the head of patrimony and marketing for the manufacture, “At the time, watches were very baroque in decoration. He [A-L Breguet] was the first to introduce a new, clean, modern design language. He applied subtly different decorations to each sector of the dial to aid in clarity.”
The 5287 uses snailing for the chrono minute counter and an amazing circular barleycorn decoration for the continuous seconds counter (note that this features a two-sided hand read off a 30-minute track). The dial receives Paris hobnail guilloché, while the hour indexes are on a circular brushed track with the tachymeter on an opaline flange. The entire dial is solid gold and a masterwork of guilloché main or hand guilloché, where these patterns are engraved using hand-guided, ancient rose-engine machines. The round case has the same fluted caseband that A-L Breguet used to decorate his pocket watches.
Now, flip the watch over and revel in the glory of the Lemania 2320. Interestingly, this is the only version of the Lemania 2320 that uses 24 jewels. Breguet also uses the swan-neck regulator but increases the vibrational speed to 3Hz.
Vacheron Constantin Calibre 1140/1141, based on the Lemania 2320 or CH 27-17P, 1989–Present Day
Since 1989, Vacheron Contantin has been able to create some of the most handsome chronographs using the 21-jewel Lemania 2320 as its base. This movement was dubbed the Vacheron calibre 1140. According to Vacheron Constantin, the 1140 was based on the 17-jewel 2310 model. But the confusion arises from the fact that when I’ve looked at calibre 1140-equipped Vacheron watches, they appeared to have 21 jewels and swan-neck regulators, leading to me believe that this work was undertaken in-house. The calibre 1141, however, uses the Lemania 2320 as its base, which comes with 21 jewels and a swan-neck regulator. Note that none of these movements had a Geneva Seal.
Over the last three decades, the manufacture has used the 1140/1141 for three models — the Historiques Chronograph, the Malte Chronograph and the Patrimony Traditionnelle, where it has also been combined with a perpetual calendar.
Of these watches, one of the most sublime is the 47100, a magnificent skeletonized version of the Patrimony Chronograph. These watches can be purchased in the secondary market for around USD 20,000 to USD 30,000, which is a considerable bargain considering their original price is four times that.
Of these watches, one of the most sublime is the 47100, a magnificent skeletonized version of the Patrimony Chronograph. These watches can be purchased in the secondary market for around USD 20,000 to USD 30,000, which is a considerable bargain considering their original price is four times that.
Although the halcyon manufacture launched its own in-house chronograph movement in calibre 3300 in 2015, it still continues to use this charming historic movement in what can be considered one of Vacheron Constantin’s most successful chronographs of all time, the magnificent Cornes de Vache which takes its name from its stylized lugs. The Cornes de Vache is inspired by the 1955 reference 6087. Amusingly, the original 35mm watch from 1955 featured a Valjoux 23 movement which measured 29.5mm as opposed to the 27mm diameter calibre 1142 of the modern watch.
The Cornes de Vache is to me one of the most desirable and iconic modern men’s dress chronographs on the market. Launched in 2015, the watch was a brilliant modernization of the smaller 6087. Says Emilie Vuilleumier, the designer who was tasked with the watch’s creation, “The original watch has very rounded lugs. But we wanted to add a more dramatic sharper profile to the edge to add a sense of dynamic tension to the overall design.” Flip the watch over and revel in the most beautiful chronograph movement ever created.
Note that the movement in the Cornes de Vache is caliber 1142. How does the 1142 differ from the 1141? Well, it is the in-house-produced version of the movement. Richemont acquired the rights to manufacture this movement when it purchased Roger Dubuis in 2008. From a technical perspective, the most obvious difference between the 1142 and its predecessor is the use of a free sprung balance wheel which is clearly inspired by the Patek Philippe CH 27-70.
Roger Dubuis calibres 56 and 65, based on the Lemania 2320 or CH 27-17P, 1995–2003
Roger Dubuis secured the rights to manufacture the Lemania calibre 2310/2320. He used this movement extensively, with his brand being the only one to feature a monopusher version of this movement.
In 1995, Roger Dubuis, a watchmaker who’d spent many seminal years at Patek Philippe and gained renown for creating the world’s first double-retrograde perpetual calendar along with Agenhor founder Jean-Marc Wiederrecht, launched his eponymous brand. His Hommage model can only be described as his expression for vintage Patek Philippe design.
He created his Lemania 2320-based chronograph in three sizes — 34mm, 37mm and 40mm — demonstrating the remarkable design adaptability of the movement. His Lemania movements received the Geneva Seal and were certified as chronometers by the observatory at Besançon. They are designated RD56 for the regular two-pusher version and RD65 for the monopusher version. I believe that Roger Dubuis was the only modern watchmaker and brand to make a monopusher version of the Lemania 2320.
Dubuis used the movement in other models, including his baroque Sympathie case which was combined with the double-retrograde perpetual calendar, and notably, the Easy Diver Chronograph, making it the only dive watch to receive the Geneva Seal. OK, here’s the important thing about the 2320 movement found in the Roger Dubuis watches. Dubuis managed to secure the rights to produce the movement in-house. In 2008, when Richemont Group bought Roger Dubuis, it obtained the rights to produce this movement.
Of the various Lemania 2320-based Roger Dubuis chronographs, my favorites are the H40 (40mm size) Roger Dubuis Hommage Chronographs. I’ve spoken at length about how, from a design perspective, I find these to be some of the most beautiful watches of the modern era, in particular related to the combination of Breguet numerals, pointed baton markers, applied dots and perfectly designed typography, as seen here on my personal watch.
The Split-Seconds Versions
Patek Philippe ref. 5004
One of my favourite fantasies is to take a Patek Philippe 5004, travel back in time, and show the creator of the Lemania 2310, Albert Gustave Piguet, the transformation of what he had conceived as a workhorse movement into what I feel is the single most beautiful and technically ground-breaking, complicated chronograph movement of all time.
The 5004 launched in 1994 is a watch that Philippe Stern had pushed his team passionately for, a journey that was not without some massive hurdles. But first let me briefly explain what a split-seconds chronograph is. It is a chronograph with two seconds hands that run together. When you press the split button, integrated in the 5004 into the crown, the split-seconds hand stops for you to record an interval time such as a lap time, while the chronograph seconds hand continues to march imperiously forward. Press the split button a second time and the split-seconds hand instantly catches up with its still running sibling, which provided inspiration for this complication’s French name, “rattrapante,” which means to “catch up.”
It is commonly known that the most challenging complication to craft is the minute repeater, a watch that plays the time in hours, quarters and minutes on wire gongs. However, while many think the tourbillon is the second most challenging watch to fabricate, experts know that this is actually the split-seconds chronograph. And the 5004 was no exception.
Says Philippe Stern, “The problem was that the Lemania 2310, or CH 27-70, was never intended to be a split-seconds chronograph. We had two major challenges. The first was the pinion for all the hands — hours, minutes, chronograph seconds and split seconds — had to be made even longer and we were really stretching the limits of what was possible. Even [with] the slightest mistake, it was easy to bend this pinion. And second thing was that the CH 27 would experience rattrapante drag each time the split-seconds function was activated.”
What is rattrapante drag? What allows the split seconds to catch up with the running chronograph seconds hand so quickly and effectively is a minute ruby roller attached to an arm and loaded with a spring. This ruby rolls around the circumference of a heart-shaped reset cam attached to the chronograph wheel. When you press the split-seconds button, a mighty pincer-like brake stops the split-seconds wheel. But at the same time, the roller is tracing the shape of the reset cam the whole time, under the load of the spring, so that the moment the split-seconds wheel is released it can jump back to the correct position. The problem is that the force exerted on the heart cam by the jewelled roller can cause the entire chronograph mechanism to slow down or even stop. This is what is known as the dreaded rattrapante drag.
Patek’s solution to this issue was both beautiful and ingenious. They created a second mechanism known as an isolator, that sits on top of the split-seconds brake. When the function is activated, the isolator lifts the return lever off the heart cam so that there is no pressure placed on it. When the split-seconds function is released, it pushes the lever back into the heart cam so that it instantly resets. This mechanism is known amongst collectors as the “Octopus”, because its shape resembles that of the multi-tentacled sea creature. The Octopus and its isolator system built on top of the venerable Lemania 2320 is a masterpiece of exquisite beauty as well as a marvel of innovative engineering.
Breguet refs. 3947 and 5947
The creation of the Patek 5004 is also interesting in that over at Breguet, a split-seconds version of the Lemania 2320 had also been created, making these the only two brands to achieve this lofty accomplishment. What is even more amazing is that this Breguet movement also featured an isolator mechanism to eliminate rattrapante drag.
As I’ve mentioned, Breguet was purchased by Nicolas Hayek in 1999. Shortly after, they started creating some very beautiful Classique Chronographs with massive hand-guillochéd gold dials using the Lemania 2320 (their version has 24 jewels). By this time, the Breguet team would have had full visibility into the 5004 and its use of the Octopus isolator mechanism. As they approached the creation of their own split-seconds chronographs, the references 3947 and 5947, it must have dawned on them that they, too, would need an isolator mechanism. And as it just so happened they already had one.
Not at Lemania but at Frédéric Piguet, which they had purchased along with Blancpain in 1992 for 60 million Swiss francs. When it comes to automatic chronograph movements, the Frédéric Piguet 1185 could very well be the greatest. It was slimmer than the rest, column-wheel activated and was the first Swiss luxury movement to feature a vertical clutch, which means that the chronograph could be left running indefinitely with no effect on accuracy. It was first launched in the manual-wind 1180 in 1987, and then shortly after, in the automatic version 1185. In 1988, Frédéric Piguet stunned the world with a split-seconds version in the manual-wind 1181 and automatic 1186. Key to the reliable function of this watch was the isolator mechanism for the split seconds, which is the very first system of this kind used on any serially produced watch.
Looking at the calibre 535N of the beautiful Breguet split-seconds chronograph reference 5947, you can immediately see the isolator mechanism sitting on top of the split-seconds brake and wheel. On further examination, it appears that this isolator mechanism is largely inspired by the one used in the Frédéric Piguet 1181/1186. Understanding the great Nick Hayek’s love for consolidation and cross-brand intellectual pollination, it seems likely that he used the best of one of his brands to find a solution for the other.
For this reason, I find the Breguet 5947 to be one of the most significant watches in modern horological history, as a tribute not just to a great movement, but also to the creative inventiveness of the Swatch Group. This is something they don’t talk about openly but it clearly exists in spades and is something very much carried on by Hayek’s grandson, Marc Hayek. Also, as they hover around the USD 30,000 range in the secondary market, the Breguet 5947s are to me some of the best values around for a truly magnificent split-seconds chronograph. Note that the 3947 has its split-seconds pusher on the upper left of the case while the 5947’s is coaxial with the crown.
Image Comparison of My Patek 5970, Vacheron Cornes de vache, Roger Dubuis H40 & a Breguet 5287 On Loan
Vacheron Constantin Calibre 1142: 21,600vph or 3Hz
Patek Philippe Calibre CH 27-70: 18,000vph or 2.5Hz
Breguet Calibre 533,3: 21,600vph or 3Hz
Roger Dubuis Calibre RD56: 18,000vph or 2.5Hz
Swan Neck vs. Free Sprung
All movements, save the Patek CH 27-70, used the swan-neck regulator of the Lemania 2320. Note that when Vacheron Constantin transitioned from the 1141 to the in-house calibre 1142, they also shifted from a swan-neck regulator to a free sprung balance wheel.
The Vacheron Constantin 1142, Patek CH 27-70 and Roger Dubuis RD56/65 all receive the Geneva Seal. One of my favourite elements of the Vacheron movement is the Maltese cross-shaped cap for the column wheel. Even though this is in high relief, I am going to assume that it still qualifies as a “cap” as seen in the other Geneva Seal watches. Note that the Vacheron calibers 1140 and 1141 were not Geneva Seal movements.
Style of Intermediate Bridge
This is a funny name because it actually is the bridge that holds the seconds wheel and the minute counter wheel. You can immediately distinguish this because of the small heart cams that are used to reset these two wheels as well as the reset levers poised just beside them. This is the bridge that holds down the wheel for the minute counter and the all-important chronograph central seconds wheel. Note that this bridge has been the subject of a great deal of artistic expression for different brands. The Patek bridge is distinctly V-shaped. The Vacheron bridge is somewhere between a V and Y shape. The Roger Dubuis bridge is fully Y- or wishbone-shaped. The Omega 321 bridge is U-shaped. The Breguet is somewhere between a U and a Y.