The Classique Hora Mundi by Breguet is the first mechanical timepiece with an instant-jump time-zone display system with synchronised date, day/night and city indications.
Breguet is now introducing a new interpretation of this sensational and award winning timepiece: the Classique Hora Mundi 5727. In place of a depiction of the globe, the dial of this 2016 edition features a “clou de Paris” hobnailing motif entirely hand-crafted on a silvered gold dial. The 24-hour indicator located between 3 and 4 o’clock has been adorned with two different types of engine-turning. Its upper part is enhanced with a flame pattern and bears the Breguet inscription, while a cross weave motif graces the lower section stamped with the watch’s serial number. The hours and minutes are displayed by means of the famous Breguet open-tipped hands, which sweep around a chapter ring bearing Roman numerals transferred on a circular satin-brushed surface.
The Classique Hora Mundi with its single set of hours and minutes hands and no subdial is unlike other GMT or dual-time watches. Its single pair of hands is linked to a mechanical memory located beneath the dial and capable of keeping track of the time in two time zones. It is thus possible to adjust the time both in one’s place of residence and in another place in the world, and to display one or the other on demand.
In order to be truly useful, a watch with multiple time zones must also provide a display of the local date along with information relating to the daytime or night time hours in the home time zone. When the Hora Mundi switches from one memorised time to another, the date – synchronised via a “tracking” calendar – along with the day/night or 24-hour indication, are simultaneously adjusted.
All this takes place without disturbing the rate of the watch, whose precision is maintained during time-setting by means of a stop-seconds system. The highly original date display is based on a dragging disc appearing through a 12 o’clock aperture able to reveal three successive dates at a time. So as to avoid any confusion when reading off the date, the Breguet watchmakers have complemented the dragging system with a retrograde hand.
The latter is hidden beneath the dial and tipped by a protruding circle that frames the current date as soon as it appears in the left-hand part of the aperture and follows it throughout the day until it disappears to the right of the aperture. At midnight, the hand bearing the circle jumps to return to the left-hand side of the aperture and frame the date of the new day that is beginning.
The mechanical self-winding movement capable of orchestrating such feats is based on Calibre 777 with a silicon escapement, equipped with an additional module. Four patent applications were filed when it was designed. The first was for a timepiece comprising a mechanism with two time zones; the second covered the display of a time zone on demand via the main set of hands; the third was for a programmable and reprogrammable mechanical memory wheel for a timepiece; and the last for a mechanism for displaying a temporal dimension by means of a dragging hand.
In terms of its exterior, this watch measuring 43 mm in diameter and 12.6 mm thick – compared with 13.55 mm for the 2011 version of the Classique Hora Mundi – is available in 18-carat rose or white gold versions. It is fitted with a sapphire crystal caseback and features a number of sophisticated touches such as a slim rounded bezel, a case band with finely fluted sides, as well as added welded strap lugs.
Model: Breguet Classique Hora Mundi 5727
18-carat white gold with delicately fluted case band
Welded lugs with screw bars
Screw-locked crown at 3 o’clock
Push piece-crown at 8 o’clock
Water-resistant to 3 bar (30m)
Silvered 18-carat gold, engine-turned
Individually numbered and signed Breguet
Hours chapter with Roman numerals
24-hour indicator between 3 and 4 o’clock
City indication at 6 o’clock
Date aperture at 12 o’clock
Breguet open-tipped hands in blued steel
Self-winding movement, numbered and signed Breguet
Instant time-zone jump with synchronised date, 24-hour and city indications
Cal. 77F0 composed of base Calibre 777 with additional plate
12 lignes. 39 jewels
55 hours power reserve
Inverted in-line Swiss lever escapement with silicon pallets
Balance frequency 4Hz
Adjusted in 6positions
Also available in 18-carat rose gold: Reference 5727BR/12/9ZU