Hi Everyone, A short while ago I made a post about a watch purchase from a dealer that was described as “serviced”, but actually wasn’t. The watch in question is a Zenith Captain Chronometer with Cal. 71 movement. This is a bit of a grail watch for me, especially one in the condition this one is in. The case is razor sharp and the milled hourglass on the caseback looks like it was machined yesterday. As there doesn’t appear to be much information about this caliber on the internet, please find some general information and some pictures from the “real” service below. So won’t talk in length about the background of the movement. In short, the caliber 71 is a caliber 133.8 with a date function. This date adds several components to the movement and changes the mainplate somewhat (more about that below). According the Ranfft, about 14.000 were made between 1954 to 1957. Some with chronometer certification and some without. The frequency of this movement is 21.600 vibrations per hour. Opening up the case of the watch we find the movement in pretty much perfect condition. No scratches or signs of mistreatment at all on the movement. I have the suspicion that this might be the first ever service. It’s a time capsule with the only remark being that the flat-polished screws for the automatic winding mechanism bridge are slightly marked from a screwdriver. All other screws are pristine. The movement looks completely dry though, and a bit dirty (in the picture you can notice the hair on the oscillating weight). This particular model has the movement fit inside a casing ring and uses an additional steel spring that pushes against the caseback. Other versions can be seen that have a spring fixed on the barrel bridge that presses against the caseback and keeps the movement in place. Removing the movement from the case we can see the dial with crisp printing. The hands also look untouched although they are covered in a layer of dirt. Taking a look at the back of the dial we see the Jean Singer signature and the 18k stamp. Now it’s time to take a look at the dial side of the movement. In this movement the hour wheel is directly driving the date driving wheel, instead of having an additional wheel in between. This means that the calendar wheel turns anti-clockwise at midnight, which is not so common. This movement does not have a quick-set function, but an interesting feature is the ability to turn the date backwards. As you can see, the date driving wheel has 2 fingers, one for advancing the date forward, one for backwards. To advance the date forward, one moves the date past twelve and then back to around 7, and repeats this process. Turning backwards until around 4-5 PM moves the date back. Removing the date-retaining plate, allows one to see the dial side of the movement. There is no fine finishing or polishing of screws on this side, but all the components are very solid and functionally well-finished. A nice detail are the 3 highly polished inserts that allow the calendar wheel to slide smoothly over the mainplate. In this movement design there is no traditional friction cannon pinion that holds the minute hand. Instead, the great wheel has an additional friction fit wheel that allows the hands to be set without damage to the geartrain. The steel wheel seen on the dial side is part of the great wheel, and it also drives the minute wheel. The minute wheel drives both the hour wheel and and the cannon pinion that holds the minute hand. The minute wheel is pressed against the hour wheel and cannon pinion by a wire spring to remove backlash. Without this additional spring tension, the minute hand might judder. I hope this explanation is somewhat clear. Moving on to the movement side, I have to admit I forgot to take pictures during this process. Anyway, it is a simple but extremely solid construction including the automatic winding mechanism. If there is anything of note I would say it is the use of 2 vertically-stacked wheels that look like winding pinions. These two wheels have Breguet teeth and are used to uncouple the manual mechanism when the watch is wound automatically. This mechanism should make the automatic winding mechanism more efficient. The above pictures are after cleaning and oiling but before the assembly of the oscillating weight. It was not necessary to do any adjustment to the flat hairspring. Without doing anything I got a delta of 11 seconds on the timing machine. As the oscillating weight obscures the movement view I decided to only assemble it after casing. The oscillating weight itself holds a click that winds the movement in one direction only (anti-clockwise). It’s a very simple but seemingly effective mechanism. I'll have to wear it to find out. Finally, the watch was fitted with a new gasket. I don't know the history of this particular watch, but I was very surprised by how little wear I found in the movement. Even in all the winding components, there was barely any traces of wear or deformation. It leads me to believe that this watch may have been kept to be worn on special occasions only, or was somehow forgotten by its owner. Despite some marks on the caseback from opening by a "watchmaker", this watch has been very lucky to escape damage to the movement during its lifetime.