Longines Pocket Watch


This Longines pocket watch has the 17.79abc calibre mechanism from around 1920. It is a higher-grade watch, as few are adjusted to temperature and two positions. It also has a separate bridge for each gear in the train and a micrometric regulator to adjust the timekeeping.

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With the plates removed, you can see the gear train, the mainspring barrel, and the set lever for adjusting the time when you pull the crown out.

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With the gears removed you can see the jewels. Few watches had jewels for the centre shaft in those days.

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Under the dial, you can see the gears for setting the time, the minute wheel and the hour wheel.

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The balance wheel has fourteen weight screws and four timing screws. The best way to adjust the timekeeping of the watch is to adjust these timing screws with the regulator in the middle until the watch keeps accurate time. Fine tuning the timekeeping is then done with the micro-regulator.

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The jewels in the gear train, except for the one for the centre shaft, are pressed in, rather than being held in place with screws. Pressed jewels were quite new back then.

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Here is a nice example of an original blue mainspring. Most of the mainsprings in watches break near the centre, in the watches I have seen, as shown in this photo. This mainspring barrel is unusual in that there is no barrel cap.

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