There are world time watches and there are repeater watches that chime the time on demand, but what about world time watches that can chime the time for any time zone? Based on a limited edition concept released in 2017, the Patek Philippe Reference 5531R World Time Minute Repeater is the first wristwatch that not only tells world time, but sounds local time for anywhere on the globe.

The place where mechanical watches best thrive today is in haute horlogerie – "high-art of watchmaking" where manufacturers can show off bleeding edge design and craftsmanship. A case in point in combining two established functions that at first seem completely incompatible.

There are number of ways of displaying world time on a watch, but one particularly successful one was developed in the 1930s by Genevan master watchmaker Louis Cottier, using a 24-hour dial with a rotating outer bezel printed with cities in the various time zones. A version developed by Patek Philippe in 1999 simplified this operation by allowing a single pusher to adjust the city disk, the 24-hour disk, and the center hour without affecting the accuracy of the watch.

The tricky bit is combining this with a repeater that can chime other than home time. World time and repeater functions have been set inside the same watch before, but these have run in parallel with one another, not in combination, so the chimes could only be for the one home time zone.

A repeater watch is one that uses chimes of different tones to sound the time on command. By pressing a button, the watch sounds off the hours in one tone, then, in a second tone, the number of quarter hours since the hour, then the number of minutes since the quarter hour. So, for example, at 5:37, the watch sounds five times for the hour, twice for the quarter hours, and seven times for the minutes.

According to Patek Philippe, the mechanism that drives these chimes isn't compatible with world time. The repeater consists of three cams or "snails" – one for each time division. The hour snail has 12 steps, the quarter snail has four steps, and the minute snail has four wings of 14 steps. These are connected to one another, so the minute snail pushes the quarter snail and a pain pushes the hour snail. Pressing the button or pusher on the case sets the chimes in motion and reads off the snail positions in turn using millimeter-size parts and springs that are so small that they're difficult to see.

The upshot of all this is that the repeater mechanism can't be merged with the world time mechanism without some fundamental redesign. For the World Time Minute Repeater, the minute and quarter snails remain connected, but the hour snail is driven by the time-zone wheel of the world time mechanism. This not only allows the chimes to operate for other zones with a pusher adjustment, but also advances the hour star with one-second accuracy.

This is all managed by the Reference 5531 World Time Minute Repeater's 462 part, 45-jewel, R 27 HU ultra-thin, automatic movement. This is made of two modules and is only 8.5 mm thick thanks to its 22K guilloched gold minirotor that is fully recessed in the bridge plane, yet has a 48-hour power reserve. It operates at 21,600 vph (3 Hz) with its Gyromax balance and Spiromax balance spring, giving it an accuracy of -3 to +2 seconds per day. The workings sport chamfered bridges with Geneva striping and a gold-plated Calatrava cross cover on the centrifugal governor of the chiming mechanism.

In addition to the hands and the German silver world time display with Geneva replacing Paris in the Central European Time Zone, the dial is divided into day/night zones and the center is dominated by artwork in cloisonné enamel with polychrome depicting the Lavaux landscape on Lake Geneva, which took almost two-weeks to create using a special kiln.

All of this is sealed in a 43.83 mm 18K rose moisture and dust resistant gold case with sapphire crystals front and back, skeletonized lugs, and a sharply slanted bezel to de-emphasize the 12.08 mm thickness. It's secured by a chocolate-brown alligator strap with fold-over clasp in 18K rose gold.

The Philippe Patek Reference 5531 World Time Minute Repeater is priced at CHF 495,000 (US$522,000).

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