The origins of the Patek Philippe Perpetual Calendar Chronograph go back to WWII, in 1941, when Patek Philippe unveiled the ref. 1518, the world’s first mass produced perpetual calendar chronograph, at what was then called ‘Swiss Watch Fair Basel’. The first Patek perpetual calendar wristwatch was produced in 1925 and the history of perpetual calendar pocket watches goes back much further, but the combination of that with a chronograph was unheard of in terms of serial wristwatch production. The watch would go through many recognizable iterations, with many notable models, but the first, the reference 1518, is very important to watchmaking history for a couple reasons.

The Design

First, comes the design of the 1518. A few aspects have endured above all on the dial of a Patek Perpetual Calendar Chronograph: the Arabic numerals, their style and placement around the dial, the day-month display or apertures at 12 o’clock, and the placement of the moonphase at 6 o’clock – creating a beautiful symmetry on the dial of the watch. A symmetry that has endured.

These are features of Patek Philippe design that have been the foundation for the aesthetics of their Perpetual Calendar Chronograph line, even going into the 21st century. Although there have, of course, been some changes. After WWII, the hour markers were changed, and in the late 1940s (presumably 1947-1948), the name ‘Patek Philippe & Co.’ was changed to simply ‘Patek Philippe’ on the dial. Nonetheless, examples of the 1518’s original design are present, even in the modern references of the Perpetual Calendar Chronograph. What’s most impressive about the design is that, in 1941, this was a complication that had never before been done in a wristwatch and fit into a mere 35mm case.

The Movement

Then there's the Caliber 13'''130 Q, based on the Valjoux 13Q which had been modified far from its origins to combine the functions of a perpetual calendar with those of a chronograph. This movement was equally significant historically as it was the basis for Perpetual Calendar Chronographs for decades later.  

The 13'''130 Q was manual winding with a power reserve of 42 hours and featured 23 jewels. It was decorated with côtes de Genève and the Geneva Seal, which for a long time was used almost exclusively by Patek Philippe and were an indication of the high finish of the movement. In addition, the 13'''130 Q was designed by Victorin Piguet with a capped column wheel and a Breguet overcoil. It was such a good movement it was also used on the successive ref. 2499 for over 30 years, it was only after the 2499, when the ref. 3970 was launched in 1986, that Patek started using a Lemania-based movement (Lemania 2310). Again, it is important to recall that in the 1940s and 1950s there was no other watch brand capable of producing a perpetual calendar chronograph or anything close. Only Audemars Piguet produced perpetual calendars, no chronograph, during the same time period! The uniqueness of the 1518 and the Caliber 13'''130 Q, or rather Patek’s unique ability to produce them, has to be taken into account not only when considering the 1518’s technological significance but also its design significance.

How Rare is the Patek Philippe ref. 1518

Apart from its design and horological significance, the 1518 is also extraordinarily rare, despite being serially produced – mass production for a perpetual calendar chronograph is far different than mass production for a Casio. In total, 281 Patek 1518s are said to have been produced between 1941 and 1954: 4 stainless steel models are known to exist, less than 60 in pink gold, and the rest are supposedly yellow gold. 

People claim that platinum models were also produced, although none have ever been recovered. It’s even been speculated that some models were produced in a combination of steel and pink gold, but again none have ever surfaced. The elusiveness of the 1518 alone is reason enough for them to go for such massive sums, especially the steel models. Steel is, of course, the rarest, but then there are also some unique models like King Farouk’s 1518

There is a lot of mystery surrounding the stainless-steel models, three of the four were made by casemaker George Croisier (which was acquired by J. P. Ecoffey in the early 1970s and eventually became Genevor S.A.) and are marked 508’473 (or 508’474, 508’475 for the second and third) on the inner caseback. 508’473 is also marked ‘1’ which indicates that it may have been the first stainless steel model made. The fourth does not have this designation and is speculated to have been made by another casemaker.

On the other hand, King Farouk was born in 1920 and the tenth ruler of Egypt from his family. The 18kt gold Patek Philippe Perpetual Calendar Chronograph ref. 1518 he owned was produced in 1944 and is still marked ‘Patek Philippe & Co.’ instead of the modern Patek Philippe. It is also engraved on the back with the Royal Crown of Egypt, a personal touch. The watch was auctioned by Christie’s in 2014 and again in 2018. Along with King Farouk there is a slew of aristocrats from around the world who were also known to sport 1518s, it was after all the epitome of watchmaking at the time.

The early 1950s marked the beginning of the end when the ref. 2499 was launched as the eventual replacement to the ref. 1518, discontinued in 1954. In a way the first Perpetual Calendar Chronograph marked a shift for Patek Philippe, from their split-seconds chronographs early 20th century to their more sophisticated perpetual calendar chronographs in the latter half of the 20th century – a shift that propelled them in the direction of new designs, innovative mechanical complications, and even using in-house movements. The 1518 set both design and technical standards, not only for Patek Philippe but even for the watch industry as whole as it was unrivaled upon its release and continues to be an inspiration today – which also speaks to the significance of Patek Philippe as a brand. As far as vintage Patek goes, almost everyone has a Perpetual Calendar Chronograph on their wish list. And all of this contributes to why the Patek Perpetual Calendar Chronograph fetches such high prices at auctions around the world. It is not only incredibly rare, but also embodies an important contribution to watchmaking history. A contribution that has been difficult to supplant for any other watch brand. Ultimately, it is a collector’s watch in every sense of the word and its historical significance should not be understated.

By: Andres Ibarguen