Le Locle, 1947

A place in the Swiss Jura with approximately 12.000 citizens. One of the most important centers of Swiss watch industry since 1700.

At the initiative of Charles Ziegels, who was ZENITH’s technical director at the time, engineer Ephrem Jobin starts with the design of a 30 millimeter chronometer caliber.
A movement that could meet market demands as well as the requirements of chronometer time keeping.

A year later – in 1948 – ZENITH presents the legendary caliber 135, which would eventually evolve in a true success story. Until 1962 a little more than 11.000 pieces are produced by the brand. In various editions, of which the flagship model “Port Royal” is definitely the most prestigious one. ZENITH returned once, with the 2000 model in 1965.

Now, more than 65 years later, it’s still one of the most beloved chronometer movements.

Ephrem Jobin was employed by ZENITH until 1954. His philosophy was “precision”. He was not only responsible for the 135. He also developed the caliber 133 hammer automatic, produced from 1948 until 1961. In the same period he came with the 133.8, which is basically a cal. 133 but runs with a higher frequency. By increasing the frequency Jobin was able to have the 133.8 certified as a chronometer, just like the 135.

In the timeframe 1950 – 1954 ZENITH won a lot of chronometer competitions. With the calibers 135, 133.8 and 40-T the brand broke record after record and received several awards. Leaving Patek, Rolex, Omega and Longines behind with empty hands. In that period, ZENITH was the absolute chronometer specialist.

At the present day Jobin (1909-2014) is still praised by collectors. After his time with ZENITH he worked for 30 years as a curator of the Muséé du Chateau des Monts au Locle.

Serial numbers

Serial numbers are of great importance to collectors as they can give more information about the origin of a watch. For the caliber 135 movement the following numbers can be distinguished:

First series: 1949-1952
3869xxx untill 4062xxx

ZENITH Cal. 135 1st series

Second series: 1954-1960
4217xxx untill 4872xxx

ZENITH Chronometer caliber 135

Third series (model 2000): 1962-1966
5362xxx tot 6326xxx

ZENITH Chronometer caliber 135 - Model 2000

Technical details

Manual winded

13”’, Dm= 30mm, H= 5mm
19 jewels
f = 18000 A/h
balance diameter 14mm

11.000 produced



In this post I analyse a Vostok 2809A movement. There are several versions of the movement 2809. https://www.watchuseek.com/f10/two-vostok-2809-puzzles-733380.html and https://www.watchuseek.com/f10/three-generations-vostok-precision-740114.html give details about some of them. It is even possible that between this articles all variation that have ever existed are covered.

But simplifying there basically 2 main versions of the 2809: 2809 and 2809A. They are equal in all respects but the first had a accuracy rate of -10/+5 sec a day and the other 30 seconds a day (see the attachment in https://www.watchuseek.com/f10/two-vostok-2809-puzzles-733380.html).

The 2809 were used in the Vostok Precision line, which said precision either in Cyrillic alphabet or Latin alphabet on the dials. The watches using the 2809A movements do not say precision on the dials (https://mroatman.wixsite.com/watches-of-the-ussr/vostok shows photos of many Vostok models including the Vostok Precision and Vostok with the 2809A movement).

The Vostok 2809 is based on the Zenith 135 calibre. But the first Vostok movements based on the 135 where the 2802 and the 2803 (https://www.watchuseek.com/f10/grandfather-russian-precision-watches-3368514.html). This movements, unlike the 2809, have a second subdial at 6 o’clock and did not stated precision on the dial.

Looking in the internet for the 2809 story, one mainly finds more or less the same story repeated in different places. My feeling is that different people repeat each other and so they are not independent sources. See for instance: https://www.nytimes.com/2007/12/07/style/07iht-rwatchruss.1.8637651.html?pagewanted=all&_r=0, https://forum.tz-uk.com/showthread.php?135755-Volna-(by-Vostok)-Chronometer, https://www.fromrussiawithwatch.com/vostok-volna-precision, https://www.watchuseek.com/f54/soviet-volna-wolna-cosc-watch-infinitime-13860.html

This story tells that (and quoting the NYT) “nobody is quite sure what happened, but the Zenith caliber 135 blueprints ended up at the Tschistopolsky factory, where a modified version was then produced called the Volna. At first glance it looks like a Zenith, but in fact the movement is a bit different. The Soviet engineers improved the Swiss design by adding three additional jewels, moving the second-hand from a subdial position to the central pinion and enlarging the balance wheel. This improved the accuracy of the watch.”

This post from https://www.safonagastrocrono.club/vostok-precision/ offers an alternative story and questions the “cold war spying” hypothesis. According with this post author “in the case of Vostok Precision, the Soviets looked at the Zenith Chronometer 135 for inspiration. I would like to point out that in most of the literature covering the history of Soviet watch-making, this ¨inspiration¨ is inevitably portrayed as ¨copy¨. In my opinion, this widespread vision is misleading. Whenever documentation has been lacking to support such claims of intellectual property theft, a lot of writers have traditionally just romanticised about spies and the Cold War.” The author continues: “Did the Soviets merely copy the Zenith patent? Or did they buy rights to it, as had already happened on many prior occasions? Moreover, after seeing many Motorola-made quartz units in Soviet quartz watches from the 1970s, I prefer to be cautious about statements of this kind, since the Soviet Union and the West traded extensively with one another even during the Cold War. Finally, in this (https://www.cia.gov/library/readingroom/docs/CIA-RDP78-03107A000100020004-5.pdf) declassified CIA document, originally from 1958, we can also see that it was not only the Soviets who spied and stole patents. There is a whole section in the piece dedicated to the Soviet watch factories.”

I find this second account more convincing because in reality to reverse engineer a watch movement is not complicated: buy one, disassemble it, take measures and produce drawings. The complicated part in copying a watch is to fabricate the machinery needed to manufacture the parts of the watch.

The next figure shows a picture of a Zenith 135 movement (taken from Zenith Chronometre, Cal. 135, circa 1950, stainless steel, for other pictures of the movement see for instance

Watch Analog watch Watch accessory Fashion accessory Jewellery

Technical data for the Zenith 135 and the Vostok 2809 is based is presented on the next table:

Second hand
Subdial at 6 o’clock​Sweep​
30 mm​28 mm​
5 mm​4.85 mm​
# Jewels
Balance diameter
14 mm​
18000 vph​18000 vph​
Source: bidfun-db Archive: Watch Movements: Zenith 135
and bidfun-db Archive: Watch Movements: Wostok 2809

It is impossible to do a thorough comparison between the 2 movements without disassembling them both, but looking at the bridge side it is possible to see some of the similarities and also some differences:

  • Both have a big balance that goes over the escape wheel bridge.
  • Both have a Reed’s regulator which is capable of very precise adjustments. (for more information see for instance https://www.vintagewatchstraps.com/blogregulators.php).
  • They both have the same kind of bridges, but the Zenith’s are more refined.
  • The train of wheels is not exactly the same.
  • Zenith’s crown wheel has 28 teeth the 2809 27.
  • Zenith’s ratchet wheel has 54 teeth the 2809 50.

In conclusion the Vostok 2809 and the Zenith 135 are significantly different.

Before we continue note that, usually, if the second wheel is in the centre then is called centre wheel and if it is off centre then is called grand wheel. In the text that follows I will these designation instead of second wheel to avoid confusion with the the arbour that carries the second hand which I will call second pinion.

The nest figure shows the train of wheels of the 2809A.

Pocket watch Gear Clock Watch Metal

The gears of the Vostok 2809 and,for comparison, Vostok 2409 are as follows:

TeethLeavesTime for one revolutionTeethLeavesTime for one revolution
Barrel wheel887.33787.09Hours
Second wheel/pinion641260601160Minutes
Third wheel/pinion6087.570109.99999999999999Minutes
Fourth wheel/pinion7086088760Seconds
Escape wheel/pinion1576.001585.45Seconds
Frequency (vph)1800019800
Hour wheel72124812Hours
Minute wheel/pinion276136123Hours
Cannon pinion121Hours
Second wheel extra pinion271Hours

The 2809 is a movement with a sweep second. There are different ways to achieve this. One is to have the harbour fourth wheel go through a hollow centre wheel, this is the architecture used for instance on the Raketa 2609 and 2623 (see for instance a previous post of mine https://www.watchuseek.com/f10/anatomy-raketa-2609-ha-4781423.html and https://www.watchuseek.com/f10/anat…sion-raketa-2609-ha-4797133.html#post47099583 for more details regarding these movements).

Another way is to have the third wheel drive both the forth wheel and a second pinion which harbour goes though an hollow centre wheel. This architecture is used for instance by the Vostok 2409 (see the next figure).

Pocket watch Watch Fashion accessory Metal

As it is possible to see in the picture above there is a tension spring attached to the barrel bridge that keeps the seconds hand from wiggling,and of course under this tension spring it is the second hand. The reason for this is that, as discussed in Vostok 2809: Finishing & Service Notes ? Nathan Bobinchak, without the spring, the pinion is only under tension when the escapement is unlocked, and is loose during the balance wheel’s supplementary arcs. This translates to a seconds hand that flutters.

See for instance https://www.watch-wiki.net/index.php?title=Central_seconds for a discussion on the indirect vs direct second hand.

Modern movements tend to use direct second hand, in that sense the Raketa movements 2609 and 2623 are better than the Vostok 24xx.

The 2809 uses an significantly different architecture. It has a grand wheel and a third wheel that drives both the second pinion and the fourth wheel. The third harbour has two wheels (see the next figure).

Brass Gear Metal

While both third wheels are in contact with the second pinion, only the top one is in contact with the fourth wheel pinion. This means only the top third wheel gets power from the escapement. This design makes sure that there is a constant tension on to the second pinion and stops it from wiggling. I am not sure if this was a design invented by the people who engineered the 2809 or is a design present in other movements of the time. But surely the 135 didn’t used this design because it’s second hand is a subdial at 6 O’ Clock.

The minute hand is also driven indirectly. The grand wheel has an extra pinion with 27 leaves (see figure below) that engages with the minute wheel which has 27 teeth.

Gear Rotor Auto part Hardware accessory

Because the grand wheels does a revolution in 1 hour, also the minute wheel makes a full turn in 1 hour. The minute pinion has 6 leaves and the hour wheel 72 teeth, so every hour 6 teeth of the hour wheel advance. As the hour wheel has 72 teeth it takes 72/6=12 hours to do a revolution.


2 balance cap jewels
1 impulse jewel
2 balance bearing jewels
2 pallet jewels
2 pallet bearing jewels
2 grand wheel bearing jewels
2 third wheel bearing jewels
1 third wheel cap jewel
2 second hand harbour and pinion bearing jewels
2 fourth wheel bearing jewel
1 fourth wheel cap jewel
2 escape wheel bearing jewels
1 escape cap jewel
2 balance cap jewels
1 impulse jewel
2 balance bearing jewels
2 pallet jewels
2 pallet bearing jewels
2 centre wheel bearing jewels
2 third wheel bearing jewels
2 fourth wheel bearing jewel
2 escape wheel bearing jewels
22 Jewels in total
17 Jewels in total

Why the use of cap jewels on third, fourth and escape wheels? Quoting from https://www.vintagewatchstraps.com/blogjewels.php: “The use of end stones or cap jewels achieves two beneficial results. The first is that they form oil reservoirs, the second is that they control the end float of the arbour. Because the end float of the arbour is controlled it does not need a square shoulder and can be made ‘conical’, a shape that prevents oil migrating along the arbour from the pivots”.

Finally more pictures of movement parts can be found in https://www.watchrepairtalk.com/topic/7385-vostok-volna-2809-precision/.

In conclusion, the 2809 has some unusual but interesting design choices. Is there any improvements in relation to the Zenith 135 (as it is claimed on the NYT article)? That I don’t know and leave it to more knowledgable people to tell.