What makes a truly great watch movement? It’s a lengthy power reserve, or perhaps a high level of hand finishing? Perhaps it was the first to incorporate a new technology, or advance old ideas into the modern age? These are the types of conversations we often have in our office, and they commonly throw-up more questions, than they do answers.

As such, we thought we would look at some of the most impactful and noteworthy in history. For the sake of this article, we’ve chosen to limit ourselves to five, though we’ll undoubtedly be looking at others in the future, aiming to make this into an ongoing series. We’ll be stripping down, deep-cleaning, re-assembling, lubricating and adjusting the Lemania 2310, the Jaeger-LeCoultre 920, the ETA 2824, the El Primero and the Rolex 3135. Each of these covers a different area of watchmaking and represents one of the many ways in which a movement can make an impact.

We’re not claiming that these five movements, and any others we may look at in the future, make-up the very best ever made, or that they feature the highest quality of finishing. However, they’ve all contributed something to the world of horology which deserves a closer look, whether it’s the noteworthy watches they’ve powered or their adaptability. We could have gone into much more depth on these, but we hope that this acts as an insight into what makes them all special. So without further wait, let’s pop the caseback open.

You probably don’t need us to tell you how important the Lemania 2310 is. This base calibre has been at the heart of some of the most noteworthy chronographs of the last eighty years or so. It was introduced by Lemania in 1942, a Swiss manufacturer most known for producing ébauches, which are essentially unbranded movements produced for other watchmakers. The project was led by their Technical Director, Albert Gustave Piguet, whose distant cousin was Edward Auguste Piguet, the founder of Audemars Piguet.

It was Omega that first commissioned Lemania to produce the ébauche, which would form the foundation of the brand’s revered calibre 321. Upon its release, it was the world’s smallest chronograph movement, measuring just 27mm in diameter and 6.74mm in height. This made it adaptable to different case styles and configurations. Beyond its convenient measurements, the Lemania 2310 was also an incredibly reliable, tough and serviceable movement. When Omega used it between 1946 and 1968, it was mainly for its track record of performance, which would eventually culminate in the Lemania 2310 accompanying astronauts to the moon.

Moreover, though manual-wind column-wheel chronographs had been prevalent during the mid-20th century, they were scarce by the time the Quartz Crisis had wreaked havoc on the Swiss watch industry. As such, in the 1980s, when brands started turning to the mechanical chronograph as a way to showcase horological craft, the Lemania 2310 was the only compelling option at their disposal. This is why it became the foundation for some of the most noteworthy pieces produced during the late 20th century, from Patek Philippe, Vacheron Constantin, Breguet and Roger Dubuis, among others. The range of watches it was integrated into – from tool watches for astronauts to perpetual calendar chronographs – speaks to the adaptability and quality of the ébauche.

It was Patek Philippe that would help cement the reputation of the Lemania 2310, by integrating it into several of its most significant models from the period. In 1985, they introduced the reference 3970. At a time when complicated watches were scarce, coming out with a perpetual calendar chronograph was an important statement of technical ability from the manufacture, whose intention it was to produce this reference in a series. Which ébauche did they choose for the chronograph line? You guessed it, the Lemania 2310. This same base movement would be used in the successive ref. 5970, as well as the split-second version of the complication, the ref. 5004. A few years later, in 1998, the manufacture also used the ébauche in their reference 5070, an unusual, but now sought-after, 42mm two-register chronograph.

Others followed in their footsteps, seeing the intrinsic quality and adaptability of the ébauche. Roger Dubuis, who spent two decades working in the complications department of Patek Philippe, decided to use the Lemania 2310 to power the Hommage and Sympathie chronographs produced by his own eponymous brand. Breguet went so far as to purchase Lemania in 1992, integrating this ébauche into some of their dress chronographs. As for Vacheron Constantin, they too chose a similar path, creating vintage-inspired two-register chronographs, as part of their Les Historiques collection.

All of these different brands finished the movement to different standards and adapted it to fit their purposes. While an Omega 321 may be spartan and utilitarian, a Patek Philippe CH 27-70 features chamfering and Geneva striping. One aspect which always changed, depending on the manufacture, was the design of the intermediate bridge. Shaped like a Y, U, V or somewhere in between all of these, this branch shaped bridge has always been a distinctive feature of the movement, often to be observed through the exhibition casebacks found on more modern pieces. Despite it being the same base movement, those who have studied the ébauche closely, can often identify the specific brand just by the shape of this bridge. From its origins as a sturdy workhorse movement, to helping revive the interest in mechanical watches in the wake of the Quartz Crisis, the Lemania 2310 certainly deserves to be included.

Another movement which played a significant role in helping the industry recover from the Quartz Crisis. When it was released in 1967, the Jaeger-LeCoultre 920 was the thinnest automatic movement in the world. In fact, it’s still the thinnest one out there with a full-sized rotor, as only micro and periphery motors have managed to beat it in the last fifty years.  

At just 2.45mm thick and 26mm wide, it appeared in horology at the seemingly perfect time. Just two years before the launch of the first Quartz watch, this calibre was set to help resuscitate a struggling industry. Despite never being used by the brand that made it, Jaeger-LeCoultre, it had its first major appearance in a model that has risen far higher than anyone would have expected, back in 1972, the Audemars Piguet Royal Oak. It was thanks to this movement’s slim profile that the first Royal Oak, the reference 5402, was able to achieve its svelte silhouette, whilst also offering the convenience of an automatic movement.

Furthermore, besides the lean profile and robustness of this calibre, perhaps its most remarkable feature is that it can accommodate nearly any complication with minimal added thickness. This is why the Jaeger-LeCoultre 920 also formed the foundation of Audemars Piguet’s automatic perpetual calendar movement from the period. Less widely known than the Royal Oak, this complicated calibre arguably played an even greater role than the porthole design, in ensuring the brand’s survival.

Launched in 1978, the reference 5548 was the world’s thinnest automatic perpetual calendar at the time, quickly becoming one of the manufacture’s signature models. As François-Henry Bennahmias, the CEO of Audemars Piguet, told us during a recent interview, “there were watchmakers at Audemars Piguet who decided to work on new watches without being told to. The boss at the time knew this approach was successful and fostered this sense of autonomy and creativity. Our modern perpetual calendar, which helped the brand survive in the midst of the Quartz Crisis, was created by watchmakers without their boss knowing about it.”

This contrarian attitude paid off, with the Quantième Perpetuel becoming highly appreciated by clients. To put things in perspective, in 1984, only 1,066 perpetual calendars were produced in Switzerland. Of those, Audemars Piguet made 675. The Jaeger-LeCoultre 920 made it possible for AP to combine the classic complication with a reliable, practical automatic movement, without compromising on the slim profile of the case. The days, Audemars Piguet are still able to use the 920, despite being independent from the Richemont Group who own the rights to it. The movement was so important to the company that, when they sold their stake in Jaeger-LeCoultre to Richemont in 2000, the use of the movement was part of the negotiations.

As if this wasn’t enough, the 920 also powered another noteworthy piece from the period, the original Patek Philippe Nautilus. There’s good reason to believe that without the thin calibre, Genta’s vision for a sport’s watch which balanced ruggedness and refinement would not have been as easy to execute. If the design were any thicker, it could be overpowering, and it would have seemed counter-intuitive to power a sport’s watch with a manual-wind movement. Patek Philippe used this 19,800 VPH movement from 1976, when the first Nautilus was launched, until 1981, when it was replaced by their in-house calibre 335 SC.

The third brand to adopt this ultra-thin movement was Vacheron Constantin, completing the so-called Holy Trinity of Swiss watchmakers. Just like the first two, Vacheron Constantin placed the 920 in their new luxury steel sports watch, the 222, designed by Jörg Hysek. With many hours having been spent pouring over the similarities and difference between the Royal Oak, Nautilus and 222, it’s amusing to think they were all almost identical from the inside. Unlike Patek Philippe, who have moved away from the ébauche, Vacheron Constantin have kept it in their current catalogue. Most notably, it has been used to ensure that the successor to the 222, the Overseas, maintains its svelte, yet sporty, profile.

Thin, reliable and adaptable, the Jaeger-LeCoultre 920 was essential to Audemars Piguet’s survival in the wake of the Quartz Crisis, with the Royal Oak and their perpetual calendar, whilst also powering a few other iconic designs along the way. Not the worst of legacies to leave behind.

Now, for a slight change of pace. This movement might not stand out for its complexity or craftmanship, yet its impact cannot be denied. Often labelled as the ultimate workhorse movement, the ETA 2824 is undoubtedly the most widely used of any of the calibres and ébauches that we’ll touch on here.

If we go by the numbers alone, it doesn’t stand out. 4.6mm thick, 25.6mm in diameter, 28,000 VPH and an average accuracy of plus or minus 12 seconds a day at best. So, why is this possibly one of the most influential movements in watchmaking today? It’s all thanks to this calibre’s bang for buck. Since it first appeared in 1961, it’s been adopted by established players such a Tudor and Longines all the way down to smaller brands like Ochs und Junior.

The 2824 can trace its roots back to ETA’s parent company, Eterna, and their calibre 1247. In 1948, they made one of the first major improvements to early automatic movements when they started using miniature ball bearings in their rotor. This innovation reduced the effects of wear and tear and solved the lubrication issues of earlier sleeve bearings. Interestingly, as an homage to this development, Eterna changed its company logo to its current design of five stylised ball bearings. Today, nearly every modern automatic movement uses a ball-bearing-based rotor, with the ETA 2824 being one of the most prominent descendants. Some argue that the relatively humble 2824, when suitably regulated, oiled and adjusted, can easily match the accuracy of movements developed in-house by established brands. More practically, the 2824 can beat quite a few of them for sheer robustness, thanks to its simple structure and resilient components.

While it isn’t worth going through every brand and model that incorporated the movement, there is a simple anecdote which perfectly summarises just how prevalent it is. Despite the dependence of the Swiss watch industry on the manufacturer, ETA recently made the decision to gradually limit, and eventually stop, the supply of this movement to companies outside of the Swatch Group. It agreed to do so in 2013, with the goal of halting all external sales in 2019. Did this motivate brands to develop in-house movements as a response? Quite the opposite. Instead, a flood of ETA “clone” movements have appeared from other manufacturers such as Sellita and Soprod. These clones are not masquerading as a 2824, but rather building their basic structure on this long-standing ébauche, in order to fill the void which it left behind.

It’s worth noting that this reliance on the ETA isn’t necessarily a negative thing. For many consumers, it provides an accessible entry point into Swiss watchmaking, as they might potentially be priced out of certain models if brands had to deal with the onerous costs of developing movements in-house. Furthermore, despite what brands might sometimes say, developing something internally doesn’t necessarily mean it’s better than a high-quality movement from an external supplier. After all, for a long time, the value proposition of Tudor was that they offered Rolex designs, with ETA movements, whilst keeping the price proportionally lower.

The ETA 2824 also comes in all shapes and sizes, with varied characteristics and modifications applied by brands. As Alex Barter, an auction house veteran at Sotheby’s and horological author put it, “the finishing on the movement in Tudors is fantastic, but as you move to cheaper brands, it can be pretty basic.” ETA also actually produce four variations of the 2824: Standard, Elaborated, Top and Chronometer, each offering technical improvements, with the last version reaching COSC standards. However, what remains constant is this movement’s ability to keep running and its ease of service.

Next, we come to a movement that has become increasingly famous in recent years. Supposedly the very first automatic chronograph movement in the world when it was announced in January 1969, the Zenith El Primero has become something of a celebrity in horological circles. Today, Zenith are relentlessly keeping their fifty-year-old movement alive, seemingly introducing new models with it every year, with 2021 being no exception. However, what makes this movement so special that, half a century after its release, it can still generate such excitement among collectors?

The genesis of the El Primero dates back to 1962, when the company decided to launch an R&D project to create the first automatic chronograph movement, with the ambition of launching it on the manufacturer’s centenary celebrations, in 1965. Instead of taking the easier route, which involved adding a chronograph module to a base automatic movement, Zenith had a more ambitious plan. The chronograph function had to be fully integrated within the mechanism and actuated by a column wheel, rather than by an easier-to-implement cam.

However, as if this wasn’t sufficiently difficult, they also wanted this movement to be the most accurate in the world, able to measure elapsed time by one tenth of a second. As anyone who has read any Zenith marketing material in recent years will know, this was achieved thanks to an extremely high frequency.

Meeting all of these lofty expectations just wasn’t possible in the early 1960s and instead of a release in 1965, it was finally announced at the very beginning of 1969. While Zenith were the first to announce, their competitors actually managed to get their movements into production sooner, hence why the title for the world’s first automatic chronograph remains disputed to this very day. Both Seiko and the Chronomatic Group were able to release their automatic chronographs prior to Zenith, who only rolled theirs out in September of the same year.

“One of the big achievements of this movement,” Barter points out, “is that it managed to integrate all of the chronograph functions and still be automatic, without becoming too chunky.” Whereas this might seem negligeable today, this was an important factor at the time, when svelte watches were the norm. At just 6.5mm in thickness, the El Primero managed to come in slimmer than the Lemania 2310, a manual-wind calibre, and the micro-rotor movement developed by the Chronomatic group the same year.

While this advancement in horology was impressive, it felt somewhat short lived, as Quartz technology was just around the corner. The mechanical chronograph would soon go from a functional tool, to an inferior relic, “making these new chronographs rather surplus to requirements,” as Barter puts it. Zenith first fit the El Primero movement inside the A384 and A386 models, but they never really took off, due to the seismic shift taking place in the industry at the time. This, in part, led to Zenith and Movado, who had formed a small group at the time, being sold off to an American company. So, while their watches were still made in Switzerland, all of the administration moved State side.

After a few years of mediocre results and a booming market for quartz-powered models, the American administrators decided that it was time to cease all production of mechanical movements, in 1975. It is estimated that around 32,000 El Primero movements were made before things ground to a stop and the presses and tools used were due to be sold off. Luckily, a brave watchmaker by the name of Charles Vermot saw the value in keeping hold of the machinery. After his request to keep some of it was denied, he decided he would have to act decisively. One night, with the help of another watchmaker, he moved 150 presses, along with an assortment of small tools and operating plans, up to the top floor of the workshop, where he hid them behind a brick wall.

The pieces lay dormant for close to a decade. Years later, when Rolex expressed an interest in using the El Primero to power a new generation of Daytonas, Vermot showed company leaders where he had saved the tooling and production notes. Satisfied the company could meet its needs, Rolex awarded the ten-year contract to Zenith. With production of the El Primero resuming in 1984, the first El Primero Daytonas were presented at the Basel Watch Fair in 1988.

An interesting side note in this story is that prior to the Rolex contract being signed, all of the remaining El Primero movements had been bought by Ebel, who wanted to add an automatic chronograph to their range. These pieces are now one of the most affordable ways to get hold of an El Primero movement from this era, which few know exist outside of the Zenith and Rolex world.

Zenith would also start producing the movement for their own watches again. Today, the El Primero has become one of the most celebrated movements in history, partially because of its historical significance, but also because of the romantic story which surrounds it. “If you were to ask a casual watch collector to name a movement,” Barter says, “they’ll more than likely say the El Primero before anything else.” This speaks to this calibre’s impact, that despite falling out of production and the company that made it, losing confidence in it, people remain aware of its importance to this day. Some even confuse its name with that of the watch, rather than the movement.

Finally, we arrive at one of Rolex’s quintessential movements. This simple, automatic calibre has been used by the crown since 1988, and though it’s now being slowly phased out by Rolex’s new generation 3235, both can still be found in the catalogue for now. The longevity of the 3135 in the brand’s collection speaks to how highly regarded it is. Though it has evolved over the past thirty years, in order to keep it relevant and modern despite its age, the core of the design is still very much with us.

Utilitarian in its appearance, you won’t find intricate finishing on a 3135, and for good reason. It’s been designed to be completely functional, which is possibly why you don’t see exhibition casebacks on any modern Rolex pieces. You won’t find this movement with complex modules bolted onto it either, attempting to make it into a multi-functional horological engine. It is concerned with one thing, and one thing alone, keeping accurate time for as long as possible. The fact that Rolex not only trust the 3135 for their daily wear watches like the Datejust, but also their Professional line, speaks to just how much resilient it can be. Easy to service, accurate and ready to take a beating.

Rolex have also managed to slowly upgrade it over the years with a series of patented inventions. These regular updates usually aren’t announced publicly, nor do they warrant giving it a new name. In an industry where many brands try to capitalise on movement upgrades as much as possible, in attempt to attract consumers, it’s telling that Rolex doesn’t need to. One such upgrade that’s worth mentioning is the addition of Rolex’s blue Parachrom hairspring, which occurred in 2000. It took five years of research by physicists and material engineers to come up with the chemical composition of the alloy and the surface treatment. As ever, the goal was reliability, with the surface of the hairspring being modified to reinforce its long-term stability, also giving it a distinctive blue colour.

Despite its relatively young age, compared to some of the other movements on this list, the 3135 has powered some legendary watches, prized by collectors the world over. Datejusts, Explorers and even members of the GMT family have all had the calibre, or a derivative of it, fitted. This movement provided the basis on which Rolex built a reputation that has eclipsed many in the modern watch world. “They do one thing, and they do it really well,” Barter tells us, and we have to agree with him. While the leaps forward that Rolex has made in its history in case and bracelet technology have been ground-breaking, the movement that has allowed all of these advances to count is the 3135.

While some may point to the two-part riveted rotor or the fact it rotates on an axel, instead of bearings, as being negatives, these could also be seen as calculated risks. While others have chosen to take different directions in these areas, Rolex has kept them in place, as they make it extremely easy to service the movement, alongside a range of other upsides. As the old adage goes, if it ain’t broke, don’t fix it. Though it may not be filled with the romance of the El Primero, or the vintage charm of the Lemania 2310, Rolex 3135 is noteworthy, nonetheless. In many ways, it has helped cement the crown as one of the most desirable brands in modern times and speaks to their consistent, reliable and utilitarian design approach.

The world of watchmaking is constantly shifting, as technology changes along with customer demands. Pinning down the exact movements that have made a difference in this ever-changing landscape can be tricky, especially as everyone comes to this with a different set of ideals. For some, the most important movement in the world is the one on their wrist, as it keeps them running on time, while others strive for horological perfection in the minutiae.

Hopefully, we have laid out a compelling case for how these five movements have made a difference. The Lemania 2310 and the Jaeger-LeCoultre 920 helped revive a struggling industry in the wake of the Quartz crisis, powering such icons as the Patek Philippe 3970 or the Audemars Piguet Royal Oak. As a time when the very idea of the mechanical watch was under threat, they played a key role in its survival. The El Primero is significant for being the first automatic chronograph movement in the world, though we’d argue its dramatic story is almost as influential in why we remember it today. Ultimately, it reminds us that watchmaking isn’t just about accuracy and performance, it’s also about romantic associations with the past.

As for the Rolex 3135 and the ETA 2824, they are both workhorse movements. No romance or technical mastery here, just two reliable calibres that have become cornerstones of an industry. One powered the modern collection of one of the world’s most prestigious brands, while the other was the beating heart of much of the Swiss watch industry. Whilst some of you may feel that we’ve missed out some noteworthy movements, we’re looking to make this an ongoing series of articles, so please do suggest any calibres which you feel may be worth mentioning in the future. We’ll hopefully keep the series ticking along for a while.