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Watch complications and movement types

The functions a watch movement can add beyond telling the time, and the ways a movement is built, each explained with how it works and how it affects fit.

Timing and travel complications

The chronograph adds a stopwatch, started and stopped by pushers while the watch keeps time. The GMT hand shows a second time zone against a 24-hour scale, and in a true GMT the local hour hand jumps on its own for travellers.

These complications add height and parts to a movement, which is why a chronograph or GMT caliber rarely drops into a case built for a plain three-hand movement.

Calendar and display complications

The date and the day-date show the calendar through apertures, their position fixed by the movement and so a key thing a donor must match. The moonphase tracks the lunar cycle on a rotating disc, and the power reserve indicator shows how much wind is left.

Each is documented here with how it works and, where relevant, which calibers carry it, so a movement can be matched on its functions as well as its size.

How a movement is built

Beyond the complications, movements differ in how they are made: automatic or hand-wound, hacking or not, small seconds or centre seconds, quartz or mechanical. Each of these choices changes the movement's dimensions and fittings.

The tourbillon and the ligne sizing guide round out the set, one a feat of finishing and the other the unit that starts every donor search.

Why this matters for a drop-in

A drop-in donor has to match not just the diameter and height of the original but its complications and its build. An automatic will not fill a case cut for a manual, and a date at 3 will not suit a dial with the window at 6.

Reading these guides alongside the fitment tool is how to tell whether two movements that share a footprint will really interchange in a given watch.

Match a caliber to a donor

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ChronographA chronograph is a watch with a built-in stopwatch, started,Automatic windingAn automatic, or self-winding, movement winds its own mainsp Date and day-dateA date complication shows the calendar date through an apert GMT and second time zoneA GMT watch shows a second time zone on an extra hand that c MoonphaseA moonphase complication shows the current phase of the moon TourbillonA tourbillon mounts the escapement and balance in a rotating Power reserve indicatorA power reserve indicator shows how much of the wound mainsp Small secondsA small seconds watch shows the running seconds on a small s Quartz movementA quartz movement keeps time with a tiny vibrating quartz cr Hacking seconds and hand-windingHacking stops the seconds hand when the crown is pulled out,Ligne and movement sizeThe ligne is the traditional unit watchmakers use to state a Movement housesWho makes these calibers

Sources: Fondation de la Haute Horlogerie · Wikipedia: Complication (horology)