Some watches seem to have long been focused on by collectors – pieces that are admired by the old guard and new wave alike, whether it is a Rolex Daytona or a Patek Philippe 2499. The level of appreciation and academic research seems to have constantly been high for these blue-chip pieces. However, others have flown under the radar for years, never attracting a lot of attention at auction or through private sales. Only recently, with the explosion of interest in the secondary watch market, and a shift in focus to more modern watches, have we seen real academic rigour being placed on these previously underappreciated watches.

The subject of this guide has firmly fallen in this second category. The Patek Philippe reference 3970 was first released in 1986, a date which places it in the early stages of neo-vintage by our definition. This era of watchmaking was one of transition and transformation, but also one that was long considered second rate by the earliest of collectors. However, along with many other neo-vintage models, the 3970 has been getting far more public recognition lately. With a number of in-depth guides detailing various aspects of the watch, and more and more examples appearing at auction, it’s clear that this is a watch on the ascendancy.

Following on from our Collector’s Guide to its sister reference, the 3940, we will focus on what makes this perpetual calendar chronograph so special. We wanted to explore the watch’s four generations, including our own research and speaking with experts and collectors of the 3970. A wide variety of unique and special pieces were made from this model, and it was seen as something of a blank canvas by those who commissioned these. Whenever they appear on the open market, we see just how versatile this reference can be.

The 3970 has surged in value in just the last few months as collectors start to value its complexity and beauty. Here, we will look into the reasons behind this overdue shift, and help shed some light on a watch that is still being learned about today.

The line of perpetual calendar chronographs at Patek Philippe reads like a line of succession to a royal family. “Historically, this combination of complications is maybe the most important one for Patek Philippe,” says Jasper Lijfering, CEO of Amsterdam Vintage Watches. Each one made their mark and is, in turn, measured against their predecessor and successor – so to understand the significance of one, you must first appreciate those which came before it. The genesis of this family is found in the ref. 1518 – something of a legend in today’s space, and one-time holder of the most expensive watch ever sold at auction. This was Patek Philippe’s first attempt to serially produce the perpetual calendar chronograph. Released in 1941, it would take the best part of half a century for another brand to achieve this same feat.

The 1518 represents a real milestone in the history of Patek Philippe. Many regard the perpetual calendar chronographs as the marquee complication of the brand, and when the 1518 was released just nine years after the Stern family took control of the company, it was clear the new owners were looking to make their mark. More than 80 years later, it would be fair to say that they were successful. Only 281 left the manufacture, with steel being by far the rarest of the metal types, with just four pieces known. This limited total number of less than 300 may seem small today, compared to modern production figured; however, to put it into context, Audemars Piguet only produced 20 double-complication wristwatches prior to 1992. To be clear, that’s not 20 different models or references, but 20 individual watches featuring double complications. At this stage, the world of watchmaking was still in its infancy when it came to industrialisation.

There was a slight crossover period between the 1518 and its successor, the ref. 2499, by roughly five years; the newer model was introduced in 1950. To have two extremely complex models in production simultaneously was a bold move by the brand, and shows their dominance in this space at the time. For many, the 2499 is the gold standard by which all other perpetual calendar chronographs are measured. It seems to tick every box for passionate collectors: rarity, complexity, model evolution and desirable unique pieces. The visual identity of Patek Philippe can be seen to grow through this reference, its four clearly defined series illustrating how the brand wanted to move its aesthetics towards modern tastes, reflecting the wider shifts seen in design around the mid century.

Only 349 ref. 2499 watches are known to have been produced during its 35-year production run. To reiterate what we said before, this can seem like a fairly limited number when we think of what the brand is capable of today, but the market was not as mature as it is now, and there was no call for these highly complex watches to be made at a higher rate. Today this rarity really plays into its favour as it drives up desirability on the open market.

The 2499 ceased production in 1985, replaced by the ref. 3970. Its sister model, the ref. 3940 perpetual calendar, was released at nearly the same time – and these two watches marked a new era for Patek Philippe watchmaking. Not only were they both examples of a massive increase in complex production numbers, but they also seem to incorporate more modern design tendencies that would help redefine what a Patek Philippe watch looked like. To illustrate the increase in scale that Patek Philippe were able to handle while producing the 3970, if you combine the amount of 1518 and 2499s produced, they still wouldn’t reach 20 percent of the total 3970s that left the manufacture.

“From a value perspective, the 3970 is the last relatively affordable Patek Philippe perpetual calendar chronograph reference,” says John Reardon, Patek Philippe specialist and founder of Collectability. “Within the pantheon of perpetual chronographs, the reference 3970 is certainly not considered as desirable as the reference 1518 or 2499, but the fact remains it is one of the three main perpetual chronographs offered by Patek Philippe in the 20th century.”

This price difference with the two that came before it, without a drop in production quality, is what drew esoteric collector Roni Madhvani to the reference. “[It’s] one of the classic, classic watches,” he says. “If you can’t afford a 2499, it’s in that league, in my humble opinion, and it’s one of the classics that Patek made. It’s a watch that’s overlooked and undervalued. For me, it’s the 2499 that I could never afford in this lifetime unless I win the lottery. And even then, at these levels I’m not sure I could afford it.”

The 3970 market has been gaining steam over the last two years, adds Reardon. “Like other ‘modern vintage’ Patek Philippes, the 3970 still represents a huge value buy these days. On average, the annual 3970 production was approximately 100 per year during the early years and topped off at 300 per year towards the end of production,” he says. “The supply is relatively low, especially with quality examples, and the demand is growing day by day. I am genuinely afraid that by the time you publish this article, the days of finding a 3970 under $100,000 will be over.”

“For me, the love of this watch line stops at the 3970,” says Lijfering. “I dislike the 5970 and 5270 that followed, not because I don’t like those watches, but because I can’t wear them. They’re too big, too robust and lack charm. They’re watches for Americans, not for connoisseurs in my opinion.” As Lijfering, many consider the 3970, the last true vintage perpetual calendar chronograph from the brand, as the aesthetics seem to change drastically once it is succeeded. Finally, he adds, “It’s important point to emphasise how much power or weight this watch carried in Patek Philippe’s line. If you make a perpetual calendar chronograph in 50 models, you’re not doing the same research and finishing and modification as you did with this because it’s a serially produced perpetual calendar chronograph. It had to be to the utmost perfection.”

We talk about both of these references with such reverence today because we know the impact they have since had on the brand and its growing recognition. However, this wasn’t always the case. “In the early 2000s, I recall seeing drawers of unsold 3970s at Patek Philippe USA,” says Reardon. “It was a different time. This was Patek’s most expensive regular production watch during this period and it was not an easy sale. For the record, it wasn’t easy to sell a Ref. 5711/1A at this time, either.”

This is a familiar story across many of the major manufactures at the time. There was a push to start creating more complex and more luxurious timepieces after the industry was ravaged by the Quartz Crisis. Today, many of these models have been classified under the banner of neo-vintage, as they often incorporate elements associated with true vintage timepieces with modern components, such as sapphire crystals and Super-LumiNova.

For Patek Philippe, this transition towards modernity meant a consolidation of their design language into a purer form, alongside an increase in production numbers in their most complex pieces, in part driven by their continued use of reliable third-party ébauches, and eventually the opening of their new manufacture in 1994. These two models are often talked about together, and were released as siblings, making up the core of Patek Philippe’s complex offering. Today, the market has been far quicker to grow its appreciation for the 3940 than the 3970. Not only has the price of the perpetual calendar increased at a faster rate, but so has the scholarship.

There are plenty of parallels to draw between these two models: not just their similar aesthetics, but their clear progression through numbered series. This evolution not only helps us delineate the rarer iterations, but can be a useful barometer for how Patek Philippe are developing their watchmaking techniques.

In today’s market, there is a lot of noise surrounding movements being produced solely in house – something that is often regarded as the only measure of quality that customers need worry about. Yet, as we have discussed before, this was not always the case. During the development of the 3970, it is easy to imagine that Henri Stern was searching for a base movement to power his new complex calibre. He certainly knew that he needed it to fit certain dimensions, have the capacity to be produced in high enough numbers, and be compatible with Patek Philippe’s own perpetual calendar module.

After the devastation of the Quartz Crisis, there was slim picking for Stern as he set about looking for a suitable calibre. Luckily, a company that had managed to stay afloat during this tumultuous time was the famed movement manufacturer Lemania. This was partly thanks to them forming the SSIH group with Tissot and Omega back in 1932, and partly due to the success of the Lemania 2310. Developed by Albert Gustave Piguet and launched in 1942, this was the smallest chronograph movement on the market at just 27mm across. Having more than proven its durability in the Omega Speedmaster since 1946, this classically designed column-wheel chronograph was the perfect fit for Patek Philippe and Stern’s needs.

We should correct ourselves here. It is commonly said that the base calibre is the Lemania 2310, but Patek Philippe actually went for the 2320, the slightly more developed model that included a swan neck regulator and 21 jewels rather than 17. Those with keen eyes and an intimate knowledge of movement construction will notice that the swan-neck regulator in the CH 27-70 Q is missing. However, we are certain that it is still based on the 2320 because the balance spring adjuster is still located on the balance cock and not protruding off the end: just one sign of the high level of modification that Patek Philippe carried out on it. “While working at Patek Philippe,” says Reardon, “it was drilled into us that the Lemania ébauches were completely disassembled and hand finished in-house to the same level of all other haute horlogerie Patek Philippe complicated watches.” This was echoed by Lijfering, “The base movement is super modified by Patek, it comes really close to an in-house Patek Philippe movement. It is interesting to see how much effort they put into this watch. They knew it was an important reference, so the movement has to be on par.”

This high level of finish is highlighted by the small Genevan coat of arms stamped on the bottom of the balance cock. This is the Geneva seal, which assures that the finish was completed to the highest standards acceptable in the canton. Patek Philippe would later stop submitting watches for the Geneva seal in 2009 when they introduced their own Patek Philippe seal. “The movement itself is beautiful,” says Lijfering. “It’s mesmerising the way Patek finished it, so I’m happy they chose to add the display caseback because it’s such a super nice movement.”

This fantastic movement also features a polished cap, placed over the column wheel – the heart of a vertical clutch chronograph movement. This is another addition by the Genevan watchmaker; in other calibres that use the same ébauche, such as Omega’s 321, the column wheel is completely exposed. You can also see the level of modification through the increased number of jewels – there are 24. This will, of course, be down to the addition of the perpetual calendar module.

Later on in this article we are going to point out everything that differentiates the four series of this watch, but first we thought it would be helpful to go over the characteristics which make it a 3970.

At 36mm, it sat perfectly between the 35mm of the 1518 and the 37.5mm of the 2499. It has been said that Stern thought this was the perfect size for this complication. This allows it to sit comfortably on most wrist sizes while still having a commanding presence thanks to its longer lugs and commanding 13.5mm height. The stepped lugs on this model are often cited as points of real design beauty and play perfectly with the depth of the concave bezel. You also see the continued use of the round pushers and Calatrava cross-stamped crown from the previous reference.

The triple register display is a classical choice that carries over from the 2499, building in further functionality without adding to dial clutter. It does this by integrating a 24-hour display and leap-year indicator inside the sub-dials at three and nine. The two apertures that sit at 12 o’clock, just above the Patek Philippe logo, display the day of the week and month. Examples have been seen in Italian, English, German and French – with French being one of the harder languages of which to find examples in.

The size of the sub-dials was also increased from the 2499, probably to help with the overall legibility of the different functions. They also sit closer to the centre of the dial. Across all four series, the 3970 features slightly recessed sub-dials, tiered on two different levels between the outer and inner indications. A similar design is found on later versions of the reference 3940, showing how Patek Philippe conceived and designed these models alongside each other.

Patek Philippe also helped this dial remain uncluttered by removing the tachymeter found on earlier 2499 models. Instead, you find a subtle seconds track, with every five seconds marked by an arrow and a small Arabic numeral. This is tracked by a seconds hand on the central arbour that is black in all metal types bar platinum. When the case is platinum, there is a matching seconds hand, often to contrast the black dial. You can also find examples of the 3970 in yellow, white and rose gold; however, they were not produced equally, nor can all metal types be found across all four series. More details on this below.

The majority of 3970s also include applied baton markers, with small squares at 3, 5, 7 and 9, and a double at 12 o’clock. We’ll touch upon these baton markers later on, as they are subject to change throughout the evolution of the model, and can be a great indicator of a special or limited variation when they deviate from this norm. It is also worth noting that while the moonphase disc on the 2499 was made out of enamel, Patek Philippe replaced it with a disc made out of sapphire glass, which is much less time- or labour-intensive to produce. This displays their desire to embrace some more modern production techniques in order to be able to produce greater numbers.

According to Le Cadran by Dr. Helmut Crott, the dials were produced by Stern Créations, as many of them feature the “S☆C” stamp on the back, as well as the “93 1521” code, which was their code for Patek Philippe. The silver colouring is obtained through a galvanic bath followed by a sandblasting process, giving the dials their subtly grained appearance.

The very first 3970s to leave the manufacture were limited to just 100 pieces. This is by far the rarest of all the series, and is extremely hard to come by today. The first series has a few defining features that mark it as an earlier watch than its successors, and appear to be hangovers from a more vintage style of production.

The first is the fact that this series was not water resistant. It is fitted with a snap-on solid caseback, so it was impossible to establish any kind of water proofness. This also means that it can be hard to find examples of this series in perfect condition, as a properly sealed watch is more likely to be better preserved in its mechanics and aesthetics.

This series can also be distinguished by the sub-dials which are always a few shades darker than the rest of the dial. This two-tone dial is another feature shared with the earliest examples of the 3940. Unfortunately, a high number of these two-tone dials were replaced during services at Patek Philippe, making the pieces in circulation with the correct recessed, two-tone subdials even lower than the production number of the first series would suggest.

Patek Philippe only produced this original series in their most classical of case metals – yellow gold. While all of them were produced in 1986, they may not have been sold that year. As Reardon said earlier, they were not the most popular watches on the market and they were one of the more expensive pieces out there. It would take some time for consumers to warm to the idea. According to Le Cadran, the first series features case numbers starting with 2824XXX and movement numbers from 875000 onwards.

Produced between 1986 and 1991, we start to see further modernisations – and considerations for what contemporary collectors wanted – in the second series. The reference number of this model technically changed to become the 3970E, where the E stands for étanche (French for waterproof). This signified that the snap-on caseback had been replaced for a screw-down one, reminiscent of the Borgel design that Patek Philippe had used in the past, although these cases were produced by Ateliers Réunis S.A., as indicated by the key 28 stamp found inside the caseback. This was one of the suppliers that Patek Philippe owned; their old building now contains the Patek Philippe Museum. The cases for the first two series were finished by hand, only increasing their desirability.

It was also possible for clients to order this watch with an additional sapphire caseback. One aesthetic change was the disappearance of the two-tone sub-dials, which were replaced with ones that matched the rest of the dial. However, it is still possible to find early examples of the second series with a two-tone dial. You will also find the full array of metal types available here, including yellow, rose and white gold and platinum. Of course, these were not made in equal amounts. It’s believed about 650 examples of the second series were produced, and the two white metals are the hardest to find.

You can also see some variation in the font used on the day and month discs from the original 100 pieces. First, the typeface had a very small serif; later, some examples use something akin to a typewriter’s font – a very clear and legible choice, yet perhaps a little less refined than before. According to Le Cadran, the second series features case numbers starting with 2828XXX, 2831XXX, 2837XXX, 2840XXX, 2846XXX, 2851XXX, 2860XXX, 2873XXX and movement numbers starting with 875XXX.

This is where the biggest aesthetic changes started to happen. The leaf – or feuille – hands of the first two series are gone, replaced with baton hands. The applied markers are also updated for ones that are pointed and faceted, matching the new hands. The dial of the third series is a brighter shade, with the printing showing a much starker contrast. This only adds to its more modern feel, as the 3970 continues to mark the interesting transition from vintage to modern.

As mentioned in the above section, the third series saw a transition when it came to the typeface used on the day and month discs. Moving from a typewriter-style font to a large, sans-serif font, which appears to be more common in this series. Along with this shift you can also observe something similar in the printing of the dial. This difference is most easily spotted when looking at the lines in both the left and right-hand sub-dials and the date numerals that encircle the moonphase. Earlier models show thicker printing on the sub-dial markers while the date numerals appear to be slightly thinner, with a dot separating the 31 and 1. As we move into slightly later examples of the third series we see thinner, more refined lines around the sub-dials at 3 and 9, and the date numerals are substantially thicker, with no dot separating 31 and 1. While our original research suggested that his changed happened at the same time as the shift in the day and month disc font, we now believe that these changes happened separately as we have seen examples where the older font is used with a newer dial. This is possibly due to the previously mentioned batch production method which was common then, causing these slight inconsistencies around the model over time. This, combined with the change in hands and markers can give this series an entirely different impression while on the wrist.

This watch saw a dramatically increased production run, with an estimated 1,350 pieces made from 1989 to 1995, in all four metals. This makes it one of the easiest variations of this model to find on the market today, all with both solid and sapphire screw-down casebacks. This abundance on the market has certainly affected how they are perceived, but it shouldn’t take away from the incredible watches they are. According to Le Cadran, the third series features case numbers starting with 2896XXX, 2900XXX, 2919XXX, 2928XXX, 2934XX, and movement numbers with 875XXX and 876XXX.

Here we see less variation, but still a clear delineation, marked by a change in the serial number ranges in the movement and case numbers. These models also came with a folding clasp made from the same metal as the case, something that often divides collectors (purists prefer the traditional pin buckle). Produced from 1994 – slightly overlapping with the third series – until 2004, when the reference ceased production, around 2,000 of the fourth series left the manufacture.

Like the previous series, these were made in all metal types, with a similar distribution across them. There are no other real aesthetic changes that make this series easy to differentiate from the third – the pointed baton markers and hands remain, and similar printing can be seen across all of them. According to Le Cadran, the fourth series features case numbers starting with 2968XXX, 2993XXX, 4010XXX, 4054XXX, 4177XX, and movement numbers with 3045XXX.

When it comes to the 3970, the topic of outliers is a significant one. The watch could easily be described as one of the greatest blank canvases that Patek Philippe has ever made, with numerous collectors adding their personal style and flair to it. Alongside these personal commissions, the brand themselves would produce a few notable limited runs.

An example of a special version of this watch that was produced by the brand and seems to have been a standard retail model – although it could just have likely been an option that buyers could select from when ordering – was the one with the integrated bracelet. Given the reference number of 3970/002, these watches did away with the sculpted lugs and attached a “beads of rice” bracelet directly onto the case. These can be found in the full assortment of case metals, and across all except the first series. Patek Philippe also delivered some models with a removable bracelet in various different styles.

Today’s collectors often focus on the way the hallmarks are presented within the regular-production 3970s. There are a few examples where the side of the lugs are stamped with what are known today as “big hallmarks”. Lijfering personally owns a 2nd series in white gold with a big hallmark, “It says 750 on the lower left lug and it’s just so eminent and prominent. You can really see it with your naked eye. Normally hallmarks don’t really change the design, but with this it really does. It’s inside a square and it’s so unlike Patek Philippe that I think it’s going to be, in the near future, a huge plus.” These assay marks would not have been under the control of Patek Philippe, or their casemakers, and so they would have been purely incidental, but today have become collectable.

The set made for the company’s 175th anniversary in 2015, known as the “London Edition”, is a true limited edition. With only five examples ever produced, you will rarely come across one of these rose-gold, black-dial pieces. Patek Philippe decided to move away from the traditional aesthetic for this model by adding in a tachymeter scale around the outside, while also opting for a single Breguet numeral at 12, with the rest of the markers in the form of applied dots. Everything else about this watch is the same as the original production run, having used new old stock cases and movements from when these stopped being made 11 years earlier.

Patek Philippe either had a stockpile of 3970 movements and cases after 2004, or they were able to continue to produce them in limited numbers, as multiple examples have since appeared on the market, having been commissioned privately years after the reference was replaced in the catalogue. There are examples from famous collectors such as Eric Clapton, or the former president of The Walt Disney Company, Michael Ovitz, to name just a few. Each of these combine elements of their personal style.

We spoke with Madhvani about his extremely rare 3970 in yellow gold, with a champagne dial, lume hands and lume markers, that was originally part of Michael Ovitz collection. “If you look at 6 o’clock, you can see his logo just there,” he says. “When I bought it, it was brand new, sealed, [and had] never been used. I used to have a great black-dial, white-gold 3970 and that was my everyday watch, but I had to sell that – and several other watches – just to be able to afford this one.” This just goes to show the excitement that these rarer pieces can generate among collectors, willing to sacrifice a number of pieces for something a bit more special. Madvahni’s special 3970 also has a tachymeter scale and a Breguet 12, both of which are features that can also be seen on pieces commissioned by Eric Clapton.

Arabic or Breguet-style numerals are not a common sight on a 3970, as this feature never appeared in the standard production, so these pieces generate great excitement when they do show up at auction. Take, for example, a yellow-gold special-order piece that was made in 2006: it has a champagne dial, full Breguet numerals and rarely seen Breguet hands. It came up for sale in late 2016 at Christie’s, and realised CHF 331,500 – a serious mark-up compared to where the market was then for all variants of the 3970.

It is also possible to find this reference with diamond markers. Only found on platinum or white gold models – and often only on those with black dials – they are hard to come by. One interesting example that we came across in our research, and which appeared at auction recently, was a box set of yellow, rose, white gold and platinum integrated-bracelet 3970s, with both the platinum and white gold containing diamond markers. This is the only box set of this kind that we could find, and it appeared at Antiquorum in 2020, but has no sold price on the online listing.

A piece that we were lucky enough to handle in the past is a platinum fourth-series example with a semi-gloss black dial. Held in one’s hand, it has a clear visual difference, and it shows that a slight shift in manufacturing process must have occurred at some point in the lifetime of the fourth series. This dial texture is one that many collectors of vintage Rolex will be familiar with.

There are a lot of reasons to love the 3970, and the attention it has received recently reflects the level of appreciation a tight group of collectors have had for it all along, just bubbling under the surface. However, there is still a lot to learn about this model and while it may never reach the heights of its predecessor, the 2499, it is still an incredibly important model in the history of Patek Philippe. It was not the first serially produced perpetual calendar chronograph, but it can be seen as an incredible leap forward in the capabilities of the brand, showing that they could ramp up their production figures with hardly a drop in quality.

While these higher production figures can seem off-putting to many collectors, as many look for rarity, for us it charts the evolution of one of the most historic watchmaking companies of all time. We are certain that there will be examples that still haven’t come into the public sphere yet, thanks to the high number of custom pieces made. Many regard the recent rise in prices for this reference as a long-overdue statement of confidence in this model, and we would have to agree. There is a lot to love about the 3970, and even more still to learn.