Close-Up: Breguet Classique 5717 Hora Mundi

The #breguet Classique Hora Mundi, in simple terms, is the first example of a mechanical timepiece with an instant-jump time zone display. All of the displays jump between time zones with the push of a button. Once you see it, the concept is so intuitive, you wonder why it has not been done before.

The Breguet Classique Hora Mundi is equipped with the 5717 self-winding mechanical movement, which is based on Caliber 777 with a silicon escapement, in this case fitted with an additional module. The dial displays hours, minutes and seconds via centrally-mounted hands. The date is at 12 o’clock, and the city or time zone indicator is at 6. A large sun/moon or day/night display rests between 3 and 4 o’clock.

The instant-jump time zone feature with fully-synchronized displays is the showstopper. This is a world-first for a mechanical watch, and indeed this timepiece has generated four patent applications. Here’s how it works:

From among the 24 available time zones, the wearer preselects two cities for which he wishes to display local time. Once set, he can instantly change all displays from one city to the other by pressing on the combined crown/pushpiece at 8 o’clock. For example, assume it is 4 p.m. in Paris on the 25th of the month. Rotating the combined crown/push-piece reveals “Paris” in the window at 6 o’clock, then the crown at 3 o’clock is used to set the hands to 4 o’clock and the date to 25, taking care that the day/night indicator shows the sun. For quick display of the local time in Sydney, the crown/push-piece is rotated to bring up the name of the Australian city in the window at 6 o’clock; the watch then automatically sets itself to Sydney time. Accurate operation during setting is ensured by a stop second system. Since the difference in time is nine hours, the hour hand will move forward by nine hours. At the same time, the date will change to the 26th and the day/night indicator will turn to show the moon. When it is 4 p.m. in Paris, it is 1 a.m. the next day in Sydney. Once the watch has been preset, the instant-jump time zone display system will instantly change all the indications – hour, date and day/night – from Paris time to Sydney time when the wearer presses on the crown/push-piece. (Photos can be enlarged with a click.)

The Hora Mundi also offers an original date display that makes use of a dragging disc. The disc appears in a window on the dial at 12 o’clock. The window is large enough to show three consecutive dates at once. To avoid any confusion in reading the date, Breguet’s watchmakers have added a tiny retrograde hand, hidden beneath the dial except for the tip, and ending in a small circle that surrounds the date as soon as it appears at the left side of the date window. The hand follows the date through the day until it disappears at the right side of the window. At midnight, the hand jumps back to the left side of the window to indicate the date of the day just beginning.

The Hora Mundi’s four patent applications claim 1) a timepiece comprising a mechanism with two time zones, 2) the display of a time zone on demand via the main set of hands, 3) a programmable and reprogrammable mechanical memory wheel for a timepiece, and 4) a mechanism for displaying a temporal dimension by means of a dragging hand.

The Breguet Hora Mundi case measures 44 mm in diameter by 13.55 mm thick, and it is available in in 18k rose gold or 950 platinum, both water-resistant to 30 meters. The hands run over a solid gold dial available in three versions: the Americas, the European and African continents, or Asia and Oceania. The dial’s periphery has a silvered and circular satin-brushed finish, a border that is hand-engraved on a rose engine, and red-gold hour markers – or platinum depending on the case version. The dial’s center, depicting a view of the globe, is stamped and hand-engraved on a rose engine to create a “wave” motif on the oceans. The oceans are then given multiple coats of lacquer and the continents are polished. On the day/night indicator, the sky is made of lapis lazuli containing numerous pyrite inclusions that look like tiny specks of gold and represent the stars. The sun and moon are made of solid gold: yellow gold for the sun, rhodium-plated yellow gold for the moon. The cover for this disc, representing a cloud and bearing the Breguet name and the watch’s serial number, is also made of silvered 18k gold and engraved entirely by hand.

Additional technical information appears below the photo.

BREGUET CLASSIQUE HORA MUNDI – SPECS
Ref. 5717BR/US/9ZU

Case: Round, in 18K rose gold with finely fluted caseband. Caseback hand-engraved on a rose engine and fitted with a sapphire crystal. Rounded lugs welded to the case, with screw-pins securing the strap. Screw-locked crown at 3 o’clock. Push-piece/crown at 8 o’clock. 44-mm diameter. Water-resistant to 3 bar (30 meters).

Dial 18k gold depicting the American continent, hand-engraved on a rose engine with a “wave” motif beneath a translucent lacquer. Silvered and hand-engraved day/night indication in 18k gold. Individually numbered and signed Breguet. Applied chapter ring with Roman numerals. City indication at 6 o’clock. Date aperture at 12 o’clock. Open-tipped Breguet hands in blued steel.

Movement: Self-winding, numbered and signed Breguet. Instant time-zone jump with synchronized date, day/night and city indications. Cal. 77F0 composed of base Caliber 777 with additional plate. 12 lignes. 43 jewels. 55-hour power reserve. Oscillating weight in 18k gold, hand-engraved on a rose engine. Flat balance-spring and Swiss straight-line lever escapement in silicon. Breguet balance wheel with four adjusting screws. 4 Hz frequency. Adjusted in six positions.

Strap: Alligator leather.

Also available with European or Asian dials and in 950 platinum with Asian, American or European dials.

This article was originally published on March 31, 2011 and has been updated.