Repair of a mechanical Must de Cartier Tank Onyx – LumeVille

Repair of a mechanical Must de Cartier Tank Onyx

The universe of dress watches has always been dominated by a large house, I am obviously talking about Cartier.

Today we are going to talk about a watch that I particularly like, the Must de Cartier Tank watch with its onyx lacquered dial.

The Must variation of the Cartier Tank was launched in 1977 to win over American customers and open up to the Asian market. This model takes the shape of the Tank LC fitted with its sapphire cabochon crown.

must cartier tank ad

The first versions were mechanical and were replaced in 1980 by quartz versions. But let’s look at the mechanical part and that in detail.


I received this watch in very good cosmetic condition, but the movement is blocked.

First step, extract the movement. The case is sealed by four screws on its sides. After removing the dial and the hands, we are in the presence of an ETA 2512-1 movement.

After complete disassembly, we can see that the rust has affected two parts of the mechanism:

– A pivot of the intermediate wheel

– The entire barrel

After cleaning the parts, we find an intermediate wheel in good condition.

The barrel and its cover are free of rust. The mainspring is replaced by a new one.

Now that all the parts are sound, the caliber can be reassembled and oiled.

After adjustment, the movement is very precise.

The movement is ready to be cased. This caliber ETA 2512-1 measures 17.2mm in diameter (7 3/4”). Here is an image that illustrates its size well:

The date of the revision is written in marker on the bottom of the case. The needles had some stains and are now clean. Dial and glass have a few minimal marks.

Let’s move on to the fitting

This Tank has been damaged by humidity. These two scenarios are possible:

– The watch has been the victim of a simple ingress of water. Indeed, its design does not make it a model of watertightness.

– The barrel assembly suggests that an unscrupulous watchmaker “overhauled” this watch without completely dismantling the movement. The liquid entered the barrel and was not dried because it was closed, thus causing all this damage.

In order to avoid the second scenario, it is essential to give your watch to a trusted watchmaker.

Today, our Tank is in great shape and she lets us know.

must cartier tank black onyx
must cartier tank black onyx


To learn more about the history of the Cartier Tank, from 1917 to today, I recommend Franco Cologni’s book “Cartier – the Tank watch” which is a nugget.

You can get it here: “Cartier – the Tank watch”

The first version of the book was recommended to me by Roni Madhvani (@roni_m_29 on Instagram), a great collector of dressy and atypical vintage watches, because this one is more complete in terms of vintage watches according to him.

You can also read Simon’s article on

must cartier mechanical tank

Some collectors do not like the Tank because it is too small or too feminine. I can only answer them with this photograph where we see the famous boxer Mohamed Ali on the right wearing a Tank Louis.

Mohamed ali cartier tank louis

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