Service: Patek Philippe Calatrava calibre 12”’-120 (1943)

It doesn’t get much more exciting for me than this – a Patek Philippe on the bench!

John from Malta sent this watch in for a service, and I’m more than happy to oblige.

In my book, watches don’t get better than this – clean design, great movement, simple, understated, and, most of all, beautiful.

First thing, I photograph the watch from all sides and inspect it before opening.

There is quite a big dent on the side of the case at 12:30 – looks like the impact was such that the springbar was pushed well into the case.

The slots for opening the back and removing the bezel have some marks, which is usual enough for a watch this age.

On the timegrapher, I note a huge amplitude, and, as soon as I move the watch to dial up position, the impulse pin knocks the bankings. This isn’t what you expect from a watch like this! Somebody must have put a mainspring into the barrel that is too strong, or something else is wrong.

My master watchmaker, George, agreed to take apart the movement with me. This not only offers me some moral support, but for the forensic work we want to do, it’s so much better to have another person to discuss findings with.

To prevent further damage to the slot, I use a proper case back opener.

A thing of beauty, with the Geneva seal well earned. Great Cote de Geneve finish, but I note that the screw heads are quite badly damaged. The screw on the fourth wheel cock stands slightly proud of the cock, and probably isn’t original.

Now the bezel comes off so I can safely remove the hands and dial before doing anything else.

The dial has some damage, but considering the age, it’s in good condition.

Now I can safely remove the hands.

Note the little groove in the case at 4:30 – this gives you access so you can lift off the dial without having to take the movement out. I like the thinking behind this feature – it makes my work easier and less risky, and somebody thought about that. For me, this is part of haute horlogerie.

The dial has its own serial number.

Having turned the screws that hold the movement in the case to the release position, I can now get the movement out.

I just love how the bridges and cocks form a wave throughout the movement. It also separates the functions out nicely, and makes it easy to see how the movement works. Just stunningly beautiful.

From here on, I use a movement holder to properly secure it.

I open the screws on the balance cock that hold the hairspring, slide the regulator pins out of the hairspring and remove the cock. That way, I don’t stress the hairspring in any way.

Looking at the balance, I notice that two of the poising screws have been filed down, and two have washers that were added. This is not something that would be done at the factory, and I interpret this as follows: the mark in the case shows that the movement must have suffered a substantial shock at one point. As the movement doesn’t have shock protected jewel assemblies, this will have broken the balance staff, which was then replaced. After replacing the balance staff, it must have been noticed that the balance wasn’t poised any more, and somebody tried to rectify that.

What strikes me as odd is that the screws that were filed down were left rough and even burred. Also, replacing the balance staff shouldn’t make re-poising the balance necessary, unless something went wrong.

I remove the cap jewels for cleaning. Perlage on the underside of the balance cock!

Before I proceed further on the top plate, I remove the components of the bottom plate. Note the two cap jewels of the balance and the escape wheel – one is white (escape wheel) and one ruby coloured. Patek would not do that – my guess here is that the cap jewel was damaged when the balance staff broke. Odd though that the new jewel (the white one), was put on the escape wheel, rather than on the balance staff.

Lovely perlage on the bottom plate – this is where the sun doesn’t shine, and only the maker and the likes of me ever get to see this! That’s why I appreciate touches like that even more.

From a conservation point of view, I quite like the white jewel. It gives me that decent hint that something was changed, and leaves a visible trace of work undertaken without damage. If done on purpose, I do agree.

Part of obtaining the Geneva Seal is not using wire springs. This is how it’s done! Note that the clutch lever is its own spring at the same time – one component. For me, minimizing component count in that way is watchmaking at its best.

Not unusual damage, but maybe unusual on such a movement. Somebody took a screwdriver that was too wide when unscrewing the detent lever screw to remove the crown and winding stem.

The balance and escape wheel cap jewels – note the huge colour difference which points to one of them having been replaced at one point. Also note that the screws have different lengths which probably isn’t original either.

With the barrel and wheel bridge removed, you can clearly see the gear train.

Notice the little drilled hole in the centre wheel. This is done at the factory to separate components into tolerance groups. From the barrel to the fourth wheel, all wheels have a single hole, so that wheels from the same tolerance group are used together. Normally, these are just scratch marks, but here, we have another sign of pure class. Perfectly drilled holes (rather sinks, as they don’t go through). Great stuff.

Even the barrel lid has perlage decoration. Something is odd about the mainspring looking through the lower opening in the lid.

The escape wheel is not polished – only where it mattes – the leaves of the pinion, the surfaces where the pallet jewels engage, and the pivots.

Beautiful mix of perlage and Cote de Geneve decoration on the top plate. There are some scratches where the pallet fork bridge is mounted, but all within what’s normal.

This is pretty shocking … and I know why the impulse pin is knocking the bankings! The mainspring must have broken at one point, and, instead of replacing it, somebody shortened it by one or two turns and bent it back on itself and wedged a piece of broken spring into that bend to form the end that locks it in the barrel. This is wrong on so many levels that it hurts. The shortened mainspring will produce too much torque, and the running time of the movement is a lot lower. On top of that, the guy used wheel grease or something similar on the mainspring.  This is beyond my understanding – a generic mainspring costs around £10. Unless you are stuck in the rainforest where you can’t order spares, you don’t do things like that. Not even to a Timex.

On top of that, somebody scribbled the movement number into the barrel. You would only do that if you would separate the movement from the barrel, e.g. to have the barrel wall reconditioned. Probably what happened here.

The underside of the pallet fork is not polished.

Whereas the top side is.

The escape wheel is also not polished.

The cannon pinion has been re tightened in several places – not quite high-end watch repair…

Very odd scratch marks on the centre wheel.

Filed-off screw on the balance wheel – even the burr was left.

And another one – not pretty.

So much for today, and thank you, George, for being with me for three hours of work!

The story continues here.



11 thoughts on “Service: Patek Philippe Calatrava calibre 12”’-120 (1943)

  1. hello sir, what do you think of this mechanical level about this patek .
    Do you think it is worth considering the current price of this beautiful time piece .
    in case of big problem the pieces are it easily foundable for a simple pay of worker ?
    how much do you ask for this service (perfectly realized) .
    in advance thank you for your reply.

  2. >Unless you are stuck in the rainforest where you can’t order spares, you don’t do things like that. Not even to a Timex.

    Oi – there is nothing wrong with Timex! My mid-70s Timex has a movement so simple and rugged that even I can service it 😉

  3. Thanks for your blog, these posts are some of the most instructive resources you can find in the internet.


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