The Ultimate Guide to the Longines Chronograph 13ZN ‘Pulsanti ad Ombrello’ or ‘Mushroom Pusher’

The Ultimate Guide to the Longines Chronograph 13ZN ‘Pulsanti ad Ombrello’ or ‘Mushroom Pusher’

When I first started collecting vintage watches, I was immediately drawn to vintage Longines. At the time, they were, in my view (and in many cases still are), unquestionably some of the best value that you could find in vintage watch collecting. The 1920s, ’30s and ’40s are widely considered by many as a golden age for watches, with many world firsts appearing during this era. And when it came to topics such as the advancement in production techniques, handmade cases, extremely high quality dials, and in-house movements with calibres finished to an excellent standard, Longines finished first in class across all categories.

In 1913, a poll commissioned by the New York Times asked the American public which brand of luxury watch they would like to own if price were no object. Of that poll, a staggering 92 percent replied that, under those circumstances, they would own a Longines. Up until the mid 1940s, a Longines watch was more prestigious and better in quality than both its Omega and Rolex counterparts, second probably only to Patek Philippe (which, incidentally, did not use in-house movements). Longines was one of the few completely vertically integrated companies at the time and, therefore, its vintage pieces are now becoming highly sought after. Very few people today realise that Longines was, in fact, the superlative chronograph and chronometer manufacture of the time.

Now under the umbrella of the Swatch Group, the modern day Longines is still very much invested in its history, producing many faithful re-edition watches. They are also blessed with a really fantastic heritage department, one that is unlike any other in the industry. Anyone can send them images and the serial number of their watch,and they can and will confirm the case, movement and (sometimes) the dial, along with information as to where the watch was originally sold, all for free!

All these factors combined make collecting vintage Longines an extremely interesting and desirable proposition.

A Brief History of the 13ZN

Longines spare parts catalogue no. 8 in French
Longines spare parts catalogue no. 8 in French

Of all the many interesting references and calibres, those with the calibre 13ZN are some of the most sought after by collectors. Produced and commercialised from 1936 to 1951, the successor to the smaller calibre 13.33Z, the 13ZN has become a cult classic and must-have for collectors of vintage chronographs from the ’30s and ’40s. Although the flyback function had been used by Longines watchmakers a couple of years prior on a very small number of examples of 13.33Z, the 13ZN was the first calibre in which the patent was filed and widely used for flyback (also known as retour en vol or the Taylor system). Calibre 13ZN Filed on 12 June 1935 and registered on 16 June 1936.

Used in a variety of cases — with semi-instantaneous counters, flyback, without flyback, monopusher and centre minutes — Longines had all the tools needed to make all the steel parts “in-house” by the mid-’30s. This was during a period where chronographs were in high demand, and very few companies had their own in-house produced movement.

The 13ZN was the first calibre in which the patent was filed and widely used for flyback. Seen here is the original patent for the flyback mechanism and the image submitted for the flyback patent. (Image: orologi.forumfree.it)
The 13ZN was the first calibre in which the patent was filed and widely used for flyback. Seen here is the original patent for the flyback mechanism and the image submitted for the flyback patent. (Image: orologi.forumfree.it)

This was the period in which chronographs had become very popular, and the issue of waterproofing or water tightness was one of the main foci for a lot of brands. The race was on to find effective solutions in regard to making these watches impervious to water. Rolex had previously introduced the Oyster case in 1926 as a regular time-only watch, and Universal Genève claimed the first waterproof chronograph in 1933 with the Colonial. But this watch still had square pushers, and it was not clear how the case around the pushers was sealed. To make a truly waterproof chronograph, a solution was needed for making the pushers watertight. A few companies were making waterproof chronograph cases around this same period; most notably, the Gallet Clamshell, the Mido Multichrono (first introduced in October 1937) and Omega with the 33.3 in 1938, to name a few. Many brands applied for various patents to combat the issue of waterproofing the pushers. However, the issue across the board seemed to be that whilst the pushers were in their “resting position” they were effectively watertight, but when used or pushed down, water might penetrate the case.

Two catalogue images from the end of the ’30s advertising a reference 4270 for sale. The words “acier hermétique tachym.” refer to the steel waterproof case of the watch and its tachymeter scale.
Two catalogue images from the end of the ’30s advertising a reference 4270 for sale. The words “acier hermétique tachym.” refer to the steel waterproof case of the watch and its tachymeter scale.

Probably the rarest and arguably the most desirable variant of Longines’ famous calibre 13ZN is the reference 4270, also known as the “Mushroom Pusher”, or “Pulsanti ad Ombrello” (umbrella pushers) for the Italian collectors, that was produced in very small numbers. One of the earliest waterproof chronographs made, a Longines first and with a unique design, the patent for the pushers was filed by Longines on February 19th, 1938. There are a few interesting and distinguishing features that have always drawn collectors to this extremely rare and unique reference. The reference 4270 was in production for five years between 1937 and 1942, with the vast majority being produced from 1938 to the early months of 1941. There were also some special cases in 1941 and 1942, which we will discuss later.

Longines Speak

To start with, I think it’s important to understand some of the terminology used by Longines:

Cliché Numbers

There are cliché numbers, or what collectors call reference numbers, that are the reference numbers as they would appear in the catalogues. This can be analogous to Rolex’s Submariner, where you’d get many references that all fall under the umbrella of the Submariner collection. Each Longines cliché has various order numbers that can be found on the casebacks, which are in effect case batch numbers.

Waterproof Pairing Numbers

Then there are also additional two- or three-digit numbers, located on the casebacks and repeated also on the lugs. Longines used these as waterproof pairing numbers, so that cases and casebacks were put correctly back together along the assembly line. I believe these to be in sequence within the order numbers, but these numbers do not necessarily correlate to the quantity of watches made within that order number.

Serial Numbers

Serial numbers are always found on the movements and sometimes also found on the case. Through the Longines Electronic Archive (LEA), they are able to use these serial numbers to correspond with the reference number (cliché) and order number on the caseback, thus confirming the watch is all matching. We now know the correct serial ranges for the various order numbers.

There is only one cliché for the 13ZN “Mushroom Pusher”, and that is the reference number 4270. There was potential for a smaller Mushroom Pusher with cliché 4813; unfortunately, the reference was cancelled.

The order numbers for reference 4270 are as follows: 2010, 2352, 2191, 2160 and 2475. These numbers typically appear on the casebacks of the watches but to confuse things a bit, the cliché number 4270 has also been seen on one caseback, and there are even a few anomalies where there is no order number at all. All these various watches with varying order numbers are very similar. Although some have small differences in details, which are unique to the order number, they are in essence the same watch.

The types of dials that these watches were born with differ in terms of style. Dials were manufactured by Stern Frères and Flückiger & Cie. (Zélim Jacot) of St-Imier.

Both made extremely high quality dials for the best watch manufacturers during the period. The dials are all the same in diameter and come in a variety of styles — some with tachymeter and telemeter scales, others with single scale or even no scale at all. Depending on the dial maker, there are small differences between the two companies’ dials, most notably in the style of fonts used.

These images show how the middle case is machined to house the collar to the pushers and inserted halfway through the case. Originally, the pushers would have cork or similarly “elastic” waterproof material to help achieve the watertightness as described in the patent.
These images show how the middle case is machined to house the collar to the pushers and inserted halfway through the case. Originally, the pushers would have cork or similarly “elastic” waterproof material to help achieve the watertightness as described in the patent.
Another image showing the crown with the two stems. This very distinctive crown was used across all order numbers of the ref. 4270. (Image: Renato Zamberlan)
Another image showing the crown with the two stems. This very distinctive crown was used across all order numbers of the ref. 4270. (Image: Renato Zamberlan)
The crown on the ref. 4270 is a very thick waterproof crown, nicknamed “Millerighe” by the Italian collectors. It has two stems, which allow for easier movement of the crown. The crown has 24 teeth, like other Longines crowns from the period. Also seen here is a close-up of the mushroom pushers.
The crown on the ref. 4270 is a very thick waterproof crown, nicknamed “Millerighe” by the Italian collectors. It has two stems, which allow for easier movement of the crown. The crown has 24 teeth, like other Longines crowns from the period. Also seen here is a close-up of the mushroom pushers.

The patent document describes the innovative way in which the pushers were to work, obviously with the main aim of keeping water out of the case and movement. How the pushers would do this can be seen in fig. 1 of the patent. A normal push “body” is fixed onto an inner rod. There is a cylindrical opening with a corresponding tube where the inner is slightly smaller than the outer, and the tightness ensures that the pusher does not spring back in the usual way.

Longines used what they termed a “waterproofing sleeve” or an elastic waterproof material, which can be squeezed and will squeeze back, thereby avoiding the spring-back you get in normal pushers, which is the point that is the most vulnerable in terms of water leakage through a standard pusher system.

To achieve this elastic sleeve, Longines used cork, which was inserted into a closed space created between the pusher body, the pusher stem and the guiding tube, so that the watertightness sleeve can be squeezed in axis when pressure is exerted, and when released, it regains its normal shape, returning the pusher and the stem to its original position.

The patent for the “waterproof pusher, for chronograph watches” or what collectors now call “mushroom” or “ombrello” pushers due to the shape.
The patent for the “waterproof pusher, for chronograph watches” or what collectors now call “mushroom” or “ombrello” pushers due to the shape.
An image from the Longines archives providing details on cliché 4270.
An image from the Longines archives providing details on cliché 4270.

Recently all-digitised, Longines is able to use their archives to find a watch using the serial number. They are also, in many instances, able to cross-reference various ledgers and invoices for the same watch, often giving collectors a great amount of detail in regard to their watch — not just where and when the watch was sold, but also information on the cases, dials and sometimes special information about the order or manufacturing process of the watch. Many of these watches were special orders and, in some cases, had gone for special waterproof testing or had specific requests regarding the dials. The digital Longines archives, of course, is an extremely useful tool for Longines collectors and, at the time of writing (June 2021), is still free for all.

Images from Longines archives, this with Cliché 4813. (Must be noted that only one example (a prototype) has ever been seen with ref 4813 and mushroom pushers, usually the ref has pump pushers).
Images from Longines archives, this with Cliché 4813. (Must be noted that only one example (a prototype) has ever been seen with ref 4813 and mushroom pushers, usually the ref has pump pushers).

Reference 4270 IN 18K Gold

With the help of the Longines archives, the mysterious logo on the dial of the gold ref. 4270 was deduced to contain the abbreviation “G.C.T”. The same logo below the Longines font can be found in another time-only watch with corresponding records at the LEA. The meaning of the logo, however, remains elusive, but it most likely refers to a retailer.
With the help of the Longines archives, the mysterious logo on the dial of the gold ref. 4270 was deduced to contain the abbreviation “G.C.T”. The same logo below the Longines font can be found in another time-only watch with corresponding records at the LEA. The meaning of the logo, however, remains elusive, but it most likely refers to a retailer.

The watch pictured here is one of two known reference 4270s, and one of five ever made, with a gold 18K waterproof case. This watch is all matching with a two-tone champagne coloured dial by Stern Frères. Although it doesn’t have the same mushroom shaped pushers, it shares many characteristics with the steel version; most notably, the hard pressure waterproof caseback and stepped case design. As it has a gold case, the lugs have a different construction to that of the steel version. Undoubtedly one of the most beautiful and important 13ZN Chronographs ever seen on the market, it is, basically, the only known example of a gold 13ZN “Mushroom Pusher” in extraordinary condition. Although the pushers aren’t the same shape, we can assume they used a similar waterproofing system as seen in Longines’ patent and in all other ref. 4270 variants. This was most likely a special order watch, as was often the case during the period when watchmakers would receive special orders from certain important retailer clients; but this is just conjecture. Also of note is the mysterious “G.C.T” logo on the dial under the Longines font. The same logo has been seen on other time-only Longines watches, as well as a Record watch, Eberhard and Movado watches, all from the same period. What the logo means is still a mystery, but it is not Greenwich Civil Time. The connection is believed to be in Italy, as all the watches (with this logo) were sent to Italy, more specifically Milano — the Longines main agent in Milan being Ostersetzer

Order 2191

An extremely rare (one of only four known to the market) reference 4270 with order number 2191.
An extremely rare (one of only four known to the market) reference 4270 with order number 2191.
The stainless steel hard pressure caseback, stamped with “Longines W. Co. Swiss” along with “Waterproof” and “Non Magnetic”. It is also stamped with the order no. 2191 along with a two-digit number that matches the number on the upper left lug (also stamped).
The stainless steel hard pressure caseback, stamped with “Longines W. Co. Swiss” along with “Waterproof” and “Non Magnetic”. It is also stamped with the order no. 2191 along with a two-digit number that matches the number on the upper left lug (also stamped).

Stainless steel hard pressure case back, stamped ‘Longines W.Co. Swiss’ along with ‘Waterproof and Non-magnetic’ stamping. Also stamped with order no 2191 along with a two-digit number matching on the upper left lug (also stamped).

Unlike order 2010, where Patent + Pending is stamped on the outer case back, here with order 2191, Modele + Depose is stamped on the inner case (as in registered patent).

The watch pictured is an extremely rare (one of only four known to the market) reference 4270 with order number 2191. Its two-tone matte silvered dial is by Stern Frères, with black Arabic numerals at 12 and 6, and baton indexes at 1, 5, 7 and 11. The dial also features tachymeter and telemeter scales, for calculating average speed and average distance, respectively.

It is interesting to note that, so far, all the known four examples of the 13ZN “Mushroom Pusher” chronographs with order number 2191 were originally sent to Chile. The serial range are also all very close (this is the same across all order numbers in that they have a specified serial range). The style of the dials can vary in their design, as is the case across all the order numbers.

The information from the Longines archives states, “Wrist chronograph in stainless steel bearing the reference 4270, the order number is 2191. It is fitted with a Longines manually wound mechanical movement, calibre 13ZN, and was invoiced on November 30th, 1940, to the company Weil, which was at that time, our [Longines’] agent for Chile.”

Order 2010

A great example of an order 2010 with a two-tone matte silvered dial by Stern Frères.
A great example of an order 2010 with a two-tone matte silvered dial by Stern Frères.
Longines W. Co. Swiss and Patent + on the watch’s caseback.
Longines W. Co. Swiss and Patent + on the watch’s caseback.

The watch showing here is a great example of an order 2010.  Probably those with order 2010 have the nicest caseback with the Patent + marking also on the outside (in reference to the patent re the pushers that was still pending mentioned above)  There are a few order 2010 that only have the order 2010 caseback mark on the caseback along with waterproof pairing no..  Interesting to note that order 2010’s do not have waterproof pairing numbers stamped on the lugs.    This one has a two-toned matt silvered dial in amazing condition, again by Stern Freres, with black Arabic numerals at 12 and 6 indexes and baton index at 1, 5 7 and 11.  Also, tachymeter and telemeter scales, for calculating average speed and distance, respectively.

Another beautiful example of order 2010, this one with an extremely rare, glossly black gilt (galvanized) dial by Stern Freres. Note the scales and indexes are gilt, whereas the Longines font has the white graphic.
2010 case-back again with Patent Pending.

Unique Example with both Cliché 4270 and Order 2010 on Caseback

As is the case with many of these watches, there are a few anomalies. This order no. 2010 has the cliché 4270 also stamped on the caseback.

A unique example of order 2010 with the cliché also on the caseback
A unique example of order 2010 with the cliché also on the caseback
A unique example of order 2010 with the cliché also on the caseback

Order 2475

Order no. 2475 is a very interesting version of the 13ZN Chronograph “Mushroom Pusher”
Order no. 2475 is a very interesting version of the 13ZN Chronograph “Mushroom Pusher”
“Longines W. Co. Swiss” and order no.2475 stamped on the caseback
“Longines W. Co. Swiss” and order no.2475 stamped on the caseback

Another very interesting version of the 13ZN Chronograph “Mushroom Pusher” is the order no. 2475. The pictured watch is one of only two 2475s seen on the market. This one has some very interesting characteristics. Note that order 2475 was the very last of the Mushroom Pushers made. Therefore, the serial numbers are late, dating to 1941. The casebacks contain the order number, and two-digit number waterproof pairing number, along with the stamping “Longines W. Co. Swiss”. Note the absence of stamping “Waterproof” and Non Magnetic” seen on other examples of the ref. 4270. Order 2475 is the only order number with spring bars instead of the fixed bars seen on all other order numbers. The hard pressure caseback, pushers and thick waterproof crown still use the same system. Interestingly, the clamping system used to secure the movement to the case is also different without the double fixing and instead with the fixing clamp just below the balance wheel (note that this same clamping system is used on the screw-back waterproof 13ZN “Tre Tacche” cliché 4974). The dial is also very nice and native, with radium indexes and single scale by Flückiger (ZJ).

Pictured here is the second known example of the 13ZN “Mushroom Pusher” with order 2475 — the second one ever seen on the market. The serial number is only six numbers away from the previous 2475 shown, and obviously it shares all the same characteristics: spring bars, same fixing clamp (like a Tre Tacche), same caseback, etc.

The second known example of the 13ZN “Mushroom Pusher” with order 2475
The second known example of the 13ZN “Mushroom Pusher” with order 2475
The second known example of the 13ZN “Mushroom Pusher” with order 2475

The information from Longines states, “Originally, the serial number identifies a wrist chronograph in stainless steel bearing the reference 4270 and order number 2475. It is fitted with a Longines manually wound mechanical movement, calibre 13ZN, and was invoiced on March 14th, 1941, to Longines-Wittnauer, which was at that time our [Longines’] agent for the USA.”

Order 2352

Ref. 4270 with order no. 2352 with a two-tone matte silvered dial by Stern Frères featuring black Arabic numerals.
Ref. 4270 with order no. 2352 with a two-tone matte silvered dial by Stern Frères featuring black Arabic numerals.

Ref. 4270 with order no. 2352 is also an extremely rare example of the watch. Around 10 examples have been seen on the market. A typical dial layout for this reference comes with tachymeter and telemeter scales. The two-tone matte silvered dial by Stern Frères features black Arabic numerals.

Another extremely rare example of the order 2352 comes with a glossy black galvanic (brass) dial by Stern Frères. The dial features tachymeter and telemeter scales with white graphic. These black galvanic dials with white graphic are among the rarest variants and also some of the most desirable, as they are nearly impossible to find, especially in the mushroom pusher case. It should also be emphasised that these cases were all produced by the piece (one by one) and, as such, there are small variations in the cases even within the same order number.

An extremely rare example of the order 2352 with a glossy black galvanic (brass) dial by Stern Frères.
An extremely rare example of the order 2352 with a glossy black galvanic (brass) dial by Stern Frères.
The original “Fab Suisse” dial is white with a tachymeter scale.
The original “Fab Suisse” dial is white with a tachymeter scale.
The ref. 4270 with a stainless steel snapback, stamped with the order no. 2352 and the words “waterproof”and“nonmagnetic”.
The ref. 4270 with a stainless steel snapback, stamped with the order no. 2352 and the words “waterproof”and“nonmagnetic”.

Another beautiful and rare example of order 2352 features not only a matte silvered dial by Stern Frères with outer blue tachymeter scale, but also the words “Fab Suisse” (“Fabrique Suisse”, or Swiss Made) in the Longines font. It has often been suggested that “Fab Suisse” on dials suggests that the watches were sent to the French market, but, at least with Longines, this was not always the case. There are watches sent to Chile, for example, that bore dials that have “Fab Suisse”, and obviously these examples have all been confirmed by the Longines archives. The example pictured here was invoiced on May 21st, 1940, to the company Sadar, which was at the time Longines’ agent in Celje (now in Slovenia). It is very interesting that the watch wasborn with a “Fab Suisse” dial, again highlighting that having “Fab Suisse” on the dial did not necessarily mean the watch was sent to France.

Order 2160

It is interesting to note that on all order 2160s, there is no Patent + mark.
This is the only order number which is engraved on the caseback and not stamped, as is the case with all the other order numbers.
This is the only order number which is engraved on the caseback and not stamped, as is the case with all the other order numbers.

The next example for cliché 4270 is order number 2160. The case of this iteration is identical to the other order numbers — a two-part case, signature stepped bezel and hard pressure waterproof caseback with lip. It also has a very nice matte silvered dial by Stern Frères, with tachymeter scale on the outer track. This example was manufactured in 1939 and sold on October 5th, 1939, to Ostersetzer, who were Longines’ main agents in Milan.

The Movement

The Longines 13ZN chronograph “Mushroom Pusher” came with two types of movement finishing, namely those with nickel finished (or rhodium plated) movements as seen on this page, and those with gilt (or galvanic gold) finishing. (see below.)

The real difference between a “standard” 13ZN reference and the 13ZN “Mushroom Pusher” is the way in which the movements are attached to the cases. The ref. 4270s have (in most cases, although there are one or two exceptions), a double fix, i.e., an extra fixing clamp, as can be seen in the image here.

The extra fixing clamp (or double fixing) unique to ref. 4270 is circled in blue. There are some exceptions — note that order 2475 has a different fixing clamp, as shown in the next image
As mentioned previously, for order 2475, the fixing clamp is just below the balance wheel. This form of clamping is also found in the 13ZN “Tre Tacche” (Italian for “three notches”), another extremely desirable variant of the 13ZN

Final Thoughts and Aknowledgements

The 13ZN “Mushroom Pusher” or “Pulsanti ad Ombrello”, rightly so, is one of the most coveted vintage watches
from the ’30s and ’40s. It is unique, both in terms of its rarity and its design, and probably the “perfect” size at 37.5mm. Even more so, it reflects a pursuit of excellence, a moment in time in which Longines strived to make the best waterproof chronograph possible. In many ways, their efforts resulted in the birth of the modern chronograph or chronometer as we know it. And to top it all off, the early Longines chronographs are, in my opinion, some of the most aesthetically beautiful watches that you can find from the period. To find a comparable waterproof chronograph from another brand, I cannot think of one, other than the Patek Philippe ref. 1463, which was not to be produced until 1949.

Ref 4270 in 18k gold, sent to Ostersetzer Milano 1941
Ref 4270 in 18k gold, sent to Ostersetzer Milano 1941

In writing this article, I had the help of a number of fellow Longines aficionados. Special thanks to Jennifer Bochud, curator of the Longines Museum, for the archive images and information; without her assistance, this article would not have been possible.

I am grateful to Glenn Mariconda and Adonya Ourshalimian for their detailed images, and to Alfredo Paramico, Auro Montanari and Andrea Foffi for the images of the gold reference 4270.

I would also like to thank Roberto Randazzo for supplying images of many of the watches, and to Guus, Tomo, Gianca and Dave for the images of their watches. Also, a big thank you to Ms Syrte for her kind help in the translation of the patent doc.

If this article interests you, there will be a longer form version published in an upcoming book by Longines collectors, Treasures of Longines, highlighting some of the most important and interesting Longines watches ever seen, so please look out for it!

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