BREGUET & Comp. No. 220 Astronomical regulator Equation du
Temps
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Lot 307
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Wednesday 25 June 2025 – 5 pm
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307
BREGUET & Comp. No. 220
Astronomical regulator “Equation du Temps”
Made between 1833 and 1836
200 × 52,5 × 32 cm
300 000 – 500 000 CHF
Please find the complete lot description on page 13.
Celebrating 250 years of Breguet (1775–2025) is more than just a milestone—it’s a tribute to a legacy of innovation, elegance, and precision that transformed the art and science of watchmaking forever.
@ Montres Breguet, 2025
Abraham-Louis BREGUET (1747–1823)
Breguet at 250 is not just about celebrating a brand—it’s about honoring the man who changed horology forever, and the generations of watchmakers who have kept that flame alive. With every tourbillon, overcoil, and engraved dial, Breguet reminds us that watchmaking is both science and art—and its heartbeat began 250 years ago.
The Birth of a Revolution (1775)
• In 1775, Abraham-Louis Breguet founded his workshop in Paris, at 51 Quai de l’Horloge.
• His genius combined scientific understanding, aesthetic beauty, and technical invention, laying the groundwork for modern watchmaking.
Innovations that Shaped Time
Over two and a half centuries, Breguet introduced or perfected numerous horological breakthroughs:
1780 Perpétuelle (self-winding)
—Among the earliest automatic watches that wind themselves through a mobile device called masselotte
1783 Breguet hands and numbers
—First time in horological history there is a new design for hands and numbers still called today Breguet 1801 Tourbillon
—Counters gravity’s effect on accuracy patented with the invention of tourbillon on 7 messidor An IX 26 juin 1801
1795 Breguet balance spring
—Enhanced isochronism on the balance spring invented and still called today Breguet balance spring 1790 Pare-chute shock absorber
—Early shock absorber for delicate pivots in the watch mechanism and still used on all watches today 1795 Sympathique clock
—Synchronized and wound a paired pocket watch automatically with the clock and presented at the national exhibition of 1798
1786 Guilloché dials
—Appearance of guilloché dials on watches, using an innovative machine also known as engineturning
A Royal Clientele
Breguet’s timepieces graced the pleasures of kings, queens, scientists, and explorers, including:
• Marie Antoinette
• Napoleon Bonaparte
• Tsar Alexander I
• Queen Victoria
• King George IV
• Duke of Wellington
• Sir Winston Churchill
The greatest figures in literature in France and elsewhere refer to Breguet, Alexandre Dumas, Balzac and Pushkin, including the famous Phileas Fogg who traveled around the world in 80 days thanks to his Breguet watch. The fame of the Breguet house is among the most famous novels.
Continued Legacy Through Generations
• Antoine-Louis Breguet, his son, carried the torch through the 19th century.
• Later descendants expanded into telegraphy and electrical instruments (Louis-Clément Breguet).
• In the 20th and 21st centuries, under various ownerships and now as part of the Swatch Group, the brand has flourished with high-complication wristwatches, preserving its DNA.
What Breguet Symbolizes Today
• Elegance in design: fluted cases, guilloché dials, blued pomme hands
• Mechanical mastery: tourbillons, chiming mechanisms, calendar complications
• Heritage meets innovation: honoring a past that changed timekeeping forever
Abraham-Louis BREGUET (1747–1823)
Abraham-Louis Breguet was a revolutionary Swiss-born watchmaker who became one of the most important figures in horological history. His innovations shaped modern watchmaking, and his influence is still deeply felt today. He is still considered today by collectors as the father of modern watchmaking.
Early Life
• Born: January 10, 1747, in Neuchâtel, Switzerland.
• Moved to Paris as a teenager where he apprenticed under several master watchmakers and studied mathematics at the Collège Mazarin.
Career Highlights
• Founded his workshop in Paris in 1775, quickly gaining a reputation for innovation, elegance, and technical mastery.
• His clientele included European royalty and aristocracy, such as Queen Marie Antoinette, Napoleon Bonaparte, Tsar Alexander I, and many others.
Influence and Legacy
• Breguet’s genius fused science, art, and practicality. His watches weren’t just functional—they were objects of beauty and status.
• His designs heavily influenced classical watch aesthetics and engineering.
• His techniques and inventions are still used or referenced in modern haute horology.
• Breguet the brand was revived and remains a premier luxury watchmaker under the Swatch Group, preserving the master’s legacy.
Death
• He died in 1823, but his son Antoine-Louis continued the business. The name Breguet has endured as a symbol of horological excellence.
Antoine-Louis BREGUET (1776–1858)
Antoine-Louis Breguet was the son of the legendary Abraham-Louis Breguet, and he played a crucial role in preserving, expanding, and modernizing his father’s horological legacy during the 19th century. While not as revolutionary as his father, Antoine-Louis was a skilled watchmaker, innovator, and businessman in his own right.
Early Life & Training
• Born: January 10, 1776, in Paris.
• From a young age, he was trained by his father, likely starting in the workshop around the age of 13 or 14.
• He inherited not just the techniques of the trade, but also the philosophy of precision, elegance, and innovation that defined Breguet’s work.
Career and Contributions
• After Abraham-Louis Breguet’s death in 1823, Antoine-Louis took over the Breguet firm, leading it for over three decades.
• He continued to produce high-quality watches, clocks, and marine chronometers, often based on his father’s inventions but with improvements and refinements.
• He preserved the reputation of the Breguet name and extended the firm’s reach across Europe and beyond.
Key Contributions:
Industrialization and Expansion
• Antoine-Louis expanded the company’s commercial operations, including overseas exports.
• Introduced a more systematized production model, balancing artisanal quality with more efficient workshop practices.
Scientific Involvement
• He was a member of the Bureau des Longitudes, a prestigious scientific body that oversaw timekeeping and navigation.
• Also served on the French Telegraph Commission, reflecting his interest in technical innovation beyond horology.
Public Service and Recognition
• Antoine-Louis was honored with numerous awards, including:
• Chevalier of the Legion of Honor
• Membership in the French Academy of Sciences
• His reputation as both a horologist and intellectual gave the Breguet firm high status during a changing technological era.
Legacy
• Under his leadership, Breguet remained one of the top watchmaking houses in Europe.
• While he was more of a refiner and manager than an inventor, his stewardship ensured the preservation of his father’s innovations, many of which could have otherwise faded in the early industrial age.
• After his death in 1858, the business passed to his son, Louis-Clément Breguet, who shifted focus toward electrical instruments and telegraphy, reflecting the times.
The importance of a regulator longcase clock
The regulator longcase clock holds a crucial place in the history of watchmaking, serving as the gold standard for precision timekeeping from the 18th to the early 20th century.
The regulator longcase clock wasn’t just a timekeeper—it was the foundation of accuracy in an age when precision was essential for science, industry, and global exploration. It helped shape the standards and techniques that define modern watchmaking today.
Here’s why it was so important:
The “Regulator” Defined
A regulator clock was designed with one purpose: extreme accuracy.
Typically, it featured:
– A central minute hand (the most prominent)
– Smaller hour and seconds subdials
– A high-quality movement, often with a deadbeat escapement
– A temperature-compensated pendulum, such as the gridiron or mercury pendulum
The Standard of Timekeeping
– Before atomic time and quartz technology, regulators were the reference clocks.
– Watchmakers, clockmakers, and observatories used them to set and adjust all other timepieces.
– In watch workshops, a regulator stood in the main room so all workers could synchronize their work.
Scientific
and Naval Importance
Regulators were key to astronomy and navigation:
– Astronomers used them to time celestial events.
– Observatories like Greenwich and Paris Observatory relied on them for standard time.
– Marine chronometers (used at sea) were regulated and checked against these master clocks.
Technological
Evolution
The design of regulators pushed horology forward:
– Development of more accurate escapements
– Advancements in temperature compensation and friction reduction
– Influenced pendulum dynamics research (e.g., Harrison’s work for longitude)
Cultural
and Horological Legacy
– Regulator clocks became symbols of precision and craftsmanship.
– They influenced the layout of dials in pocket watches and wristwatches, especially in “regulator-style” watches today.
– Many famous clockmakers, including Breguet, John Arnold, Ferdinand Berthoud, and George Graham, made or used regulator clocks in their workshops.
History behind Breguet regulator clocks
The exact number of regulator clocks produced by AbrahamLouis Breguet or finished by his son, Antoine-Louis Breguet, is not precisely documented, but based on known archives and surviving examples, it is extremely small—likely very few true regulator longcase clocks were made personally under their supervision. Of the 45 regulators listed in the Breguet archives, no more than 15 are long case regulators.
Here’s what we know:
– Breguet’s focus was primarily on watches, marine chronometers, and table clocks, not longcase regulators.
– However, a few precision regulator clocks were indeed made for scientific use or special commissions.
– The Breguet archives list several high-precision clocks that could be categorized as regulators, many of which were:
– Wall-mounted or table formats, not necessarily longcase
– Equipped with compensated pendulums, remontoire escapements, or other advanced mechanisms
Notable Examples:
– One of the most famous is the Breguet Regulator No. 386, a precision wall regulator delivered to the Paris Observatory in 1814.
– Many were produced in collaboration with or finished by his son, Antoine-Louis Breguet, who continued the workshop after A.L. Breguet’s death in 1823.
Significance in Breguet’s history
This clock exemplifies Breguet’s commitment to precision and innovation in horology. The use of dual movements and pendulums to enhance accuracy reflects his pursuit of perfection in timekeeping. The inclusion of temperature regulation mechanisms further demonstrates his attention to environmental factors affecting clock performance.
The clock’s presence in the Royal Collection underscores the high esteem in which Breguet’s work was held by European royalty, highlighting the historical bond between Breguet and the British monarchy.
The firm exhibited this double pendulum clock in 1819 which was destined for ‘the King of England’. With George III’s failing health this proved not to be possible. However, after the death of the King, Antoine-Louis Breguet sent a drawing accompanied by a detailed description to George IV, who already had Breguet’s ‘Sympathique’ synchroniser clock and watch.
The clock was delivered from the Custom House to Carlton House on 19th September 1825 where it stood at the top of the Grand Stairway. Antoine-Louis received payment of £ 1,115 in July 1827.
“This unique work is the most perfect and extraordinary thing we have done, both for its composition and its fine execution …”
Antoine-Louis
Breguet, October 1825
In a covering memorandum dated 3rd October 1825 Antoine-Louis recorded ‘Cet ouvrage unique est ce que nous avons fait de plus parfait et de plus extraordinaire, tant pour la Composition que pour sa belle exécution,..’.
Included in the Pictorial Inventory of 1827–33 –RCIN 934776. The inventory was originally created as a record of the clocks, vases, candelabra and other miscellaneous items from Carlton House, as well as selected items from the stores at Buckingham House, the Royal Pavilion, Brighton, Hampton Court and Kensington Palace for consideration in the refurbishment of Windsor Castle.
Here are some notable examples of Breguet regulator clocks that highlight the craftsmanship and innovation of Abraham-Louis Breguet:
BREGUET
Paris Observatory Clock – 1814
The Breguet Regulator No. 386 is a remarkable timepiece crafted by Abraham-Louis Breguet, exemplifying his dedication to precision horology.
Delivered to the Paris Observatory in 1814, this regulator clock was designed to serve as a reference standard for timekeeping.
Design: The clock features a wall-mounted design, emphasizing functionality and accuracy, aligning with the observatory’s requirements for a precise timekeeping instrument.
Dial Configuration: True to regulator clocks, it showcases a prominent central minute hand, with separate sub-dials for hours and seconds, facilitating precise time readings.
Escapement Mechanism: Breguet incorporated a constant-force escapement, ensuring consistent energy delivery to the timekeeping mechanism, thereby enhancing accuracy.
Pendulum: Equipped with a gridiron pendulum, designed to compensate for temperature variations, maintaining consistent oscillation rates crucial for precise timekeeping.
The delivery of Regulator No. 386 to the Paris Observatory underscores Breguet’s esteemed reputation among scientific institutions of the time. His appointment as Horologer to the French Royal Navy in 1815 further highlights his contributions to precision timekeeping.
This timepiece stands as a testament to Breguet’s innovative spirit and his commitment to advancing horology, influencing subsequent developments in precision timekeeping instruments.
BREGUET
Royal Astronomical Clock – 1819–24
This regulator clock stands as a testament to Breguet’s enduring commitment to precision and design excellence in horology. The Royal Collection Trust houses an exceptional floor-standing astronomical clock crafted by Breguet et Fils between 1819 and 1824. This masterpiece exemplifies the ingenuity and precision characteristic of Breguet’s horological creations.
Case: The clock is encased in mahogany and glass, adorned with gilt bronze moldings, and features a projecting cornice and plinth.
Movements: It comprises two independent but identical movements, each with silvered dials indicating apparent and mean time, the month, and the day. Notably, the second hand on the right dial moves anti-clockwise.
Pendulums: The clock features two identically constructed pendulums with zinc and steel compensation and brass bobs. Each pendulum swings in the opposite direction to the other, ensuring, by sympathetic action, that both movements remain extremely accurate; any error in timekeeping by one is reduced by the other.
Temperature Regulation: The base includes a compartment for burning charcoal, linked to a zinc chimney running behind the mechanisms. This feature was intended to maintain a constant temperature within the case.
THE BREGUET Royal Astronomical Clock (1819–1824)
BREGUET & Comp. No. 220
Astronomical regulator “Equation du Temps”
Made between 1833 and 1836, in the Collection of the Count di Montalvo y Nunez del Castillo, acquired on October 28, 1847 for 4,000 francs it was then reacquired by Breguet in 1849 and returned to the workshop. Presented at the Exposition Universelle in Paris in 1855, since then in private collections. Astronomical regulator with simple calendar, equation of time and minute striking on bell Case: Shaped mahogany, two pieces, front door opens with a blade system, the release being made on a gilt rod on the right side of the cabinet. Door mounted on two pivots, top and bottom. Balance wheel premounted on a large brass bracket, itself screwed to the back of the case. Movement also screwed onto the latter.
Dial: Silvered brass. Main dial in 5 pieces, each assembled with screws to a brass base plate. Outer ring indicating the hours in Roman numerals and a railroad minute track with an oversized line every 5 minutes. The hours and minutes are bordered on both sides by a saute piqué guilloché pattern. Seconds ring revealing the clock escapement and numbering every tens in Arabic numerals, bordered by two lines guillochage en sauté piqué. Railway minute track. Equation of time indicated on a portion of the barleycorn guilloché dial,
completed by a railroad minute track and saute piqué pattern over ~180°. Numerals from 45 to 15 minutes. The rest of the dial is closed by two halfmoons, each pierced to accommodate the winding squares. Engravings filled with black wax. Silver-plated brass disc with annual wheel indicating the months and tens of days. Opening of 6 arms and inclined teeth on the outside. Standardtype Breguet hands, with rounded bodies and flat ends indicating hour/minute/ seconds/equation of time/dates of the month. Signature “BREGUET/LE SOLEIL AVANCE/LE SOLEIL RETARDE”
Movement: Brass with plates, assembled by 5 pinned pillars 200 × 370 × 150 [mm]. 39 mm between plates on the back plate: Breguet & Compie No. 220 two drive wheels with block weights in the capital and descending into the false bottom of the casing. 43-day power reserve with jeweled Graham anchor, semi-polished compensating pendulum, complications: simple calendar, equation of time, and minute strike on bell. The movement is driven by weights, concealed in the false back of the sheath. The escapement is a jeweled Graham-style lever escapement. It supports a heavy compensating balance mounted on a leaf spring suspension. The clock simultaneously displays the hour, minute, second, date, and equation of time using a hand. The movement also features a minute-bell striking mechanism. This can be stopped on demand using selector. The back plate is signed “Breguet & Compie N°220”
Dimensions: 200 × 52,5 × 32 cm
Remarks from MIH restoration report:
– Item sought on November 18, 2013.
– Accepted quote received on March 4, 2014.
– Work completed in November 2014, extended to summer 2015.
Provenance:
Between 1836 and 1847 used as a reference watch at the workshops of A.L. Breguet
Sold to Comte de Montalvo y Nunez del Castillo on October 28,1847, for 4,000 francs
1849 bought back by Breguet, again at atelier
presented at the first French “Exposition Universelle” in Paris 1855 1863 sold to private collector, probably UK
Antiquorum 11. Nov. 2001, Lot 35 Private Collection, Belgium Koller, 2. Dec. 2010, Lot 1198 Swiss Private Collection
Identity card and description from the complete overhaul made upon request of actual owner at the workshops of MIH (Musée International Horlogerie) at La Chaux-de-Fonds, Switzerland.
300 000 – 500 000 CHF
The provenance behind the regulator “Equation du Temps”
This regulator executed between 1833 and 1836 was in Breguet’s workshop from 1836 until 1847, with one two-year exception: from 1847 to 1849 it was owned by Comte de Montalvo. On July 31, 1849, the regulator clock was then returned by the Count in exchange for another clock No. 233 and remained until 1863 when it was then sold to a private collection.
Belonging in the Collection of the Count di Montalvo y Nunez del Castillo, acquired on October 28, 1847 for 4,000 francs it was then reacquired by Breguet in 1849 and returned to the workshop. Presented at the Exposition Universelle in Paris in 1855 it was then acquired in 1863 by a private collector, then privately owned since it was auctioned at Antiquorum on November 11th, 2001 and then finally presented at Koller auction on December 2, 2010, remaining since then in same private hands.
The first Count de Casa Montalvo was Ignacio Montalvo (1748–1795), who, as an aspiring member of the family, moved in the highest circles of the Cuban nobility. With his business partner, F. Arango y Parreno, he traveled throughout Europe—England, Spain, and France—in search of innovative ways to produce sugar in Cuba. The fourth Count Montalvo was Don Juan Montalvo y Nunez del Castillo (1797–1859). Due to the internal political conflicts between the various noble families in Cuba, he spent most of his life in Europe, owning land in Sardinia.
The horological importance of the Breguet regulator “Equation du Temps”
What is remarkable about this long case regulator with equation of time is its craftsmanship. Its manufacture was most probably entrusted to H. Gravant, Breguet’s mechanic. H. Gravant was responsible at the time for the completion of many of his clocks and was considered the highest-paid specialist. The name Gravant was first mentioned in Breguet’s registers in 1817, when he completed the Breguet Pendule Astronomique No. 3144.
The Breguet Pendule Astronomique No. 3144, crafted by Breguet & Fils, was sold to Monsieur Ducom on November 10, 1817, for 800 Francs. This exceptional mahogany, weightdriven, floor-standing astronomical regulator clock features an eight-day movement and is distinguished by its center seconds and a pendulum calibrated for both sidereal and mean time.
The problem of such strong oscillations and the resonance of the pendulum had already been addressed by Breguet before, with the double pendulum of watches No. 3177 and No. 3671, which were sold to King Louis XVIII and King George IV respectively and have largely influenced his work in the area of watchmaking precision.
The design and precision of regulator “Equation du Temps”
The pendulum’s innovative design underscores Breguet’s commitment to precision and horological advancement. This clock exemplifies the meticulous craftsmanship and technical ingenuity that have become synonymous with the Breguet name.
To ensure that the balancing mechanism does not interfere with the precision of the clock, it was designed so that this mechanism only engages for a short time once every 24 hours. The rest of the time the mechanism is disengaged and the movement only moves the hands. The regulator clock was designed to run for three months. This long running time is ensured by two weights located on either side of the clock and hidden in the double wall of the case. This creates the impression that the clock is driven by an invisible hand. The weights are connected by two cylinders that drive the central gear. Another special feature of this grandfather clock is that it can strike every minute.
The exhibition and research from MIH at La Chaux-de-Fonds
Our regulator was lent to the museum of La-Chaux-de- Fonds MIH and is accompanied by a detailed report illustrating its historical importance for scholars. This clock remained at La Chaux-de-Fonds MIH from 2014 until 2015 and was completely overhauled under the supervision of scholar Pr. Dr. Ludwig Oeschlin.
Key features of pendule Astronomique No. 3144:
Case: The clock boasts a rectangular mahogany case with a hinged glazed door secured by a lock. Its heavy wooden back is mounted with a substantial gilt brass bracket for the pendulum suspension and two movement mounting brass brackets. An ormolu bezel adorned with palm leaf decorations enhances its aesthetic appeal.
Dial: The white enamel dial displays radial Roman numerals, complemented by an outer minute and seconds track. It is equipped with blued steel Breguet hands.
Movement: Housed within a circular brass casing, the full-plate movement includes a barrel with maintaining power, driven by a heavy brass weight and counterweight. The four-wheel train features a modified Graham dead-beat escapement with adjustable steel pallets, with the escape wheel positioned at the center of the back plate.
Pendulum: A distinctive feature is its second-beating pendulum, constructed with two wooden rods and a heavy brass bob. Uniquely, a secondary brass bob is mounted between the wooden rods, allowing micrometric adjustments for both mean and sidereal time. This design enables precise calibration by raising or lowering the bob as required.
BREGUET & Comp No. 220
Astronomical regulator, calendar, equation of time, and minute strike on bell, this timekeeper is in a cabinet predominantly made of solid oak veneered with mahogany. The mechanism of this clock simultaneously displays the hours, minutes, seconds, and equation of time on the main dial. Below, a silvered disc displaying the months of the year allows the date to be read via a fixed hand. The minute strike mechanism can be stopped on demand using a selector. Jeweled Graham-style lever escapement. The operating time is approximately 43 days. The clock is signed Breguet & Comp which was used after his son retired in 1833.
According to Breguet’s archives, the execution of the clock was entrusted to H. Gravant, Breguet’s mechanic. Gravant was responsible for the creation of a large proportion of his watches and was considered the highest-paid specialist. For more details, see the “identity sheet” of the Musée International d’Horlogerie, 2015.
Technical infos and research made on equation of time
Of the 45 regulators listed in the Breguet archives, no more than 15 are long case regulators. This one is extremely rare because of the equation of time. What is an Equation of Time? The equation of time was developed to explain and compensate for the discrepancy between true solar time and mean solar time.
The true solar day is the length of time between one local noon, when the sun is highest, and the next. The length of this day is not always 24 hours, as the hours between sunrise and sunset are not always the same. The variable rate of the true solar day is due to two factors: 1) the Earth’s rotation around the Sun is an irregular elliptical course and 2) the tilt of the Earth’s rotation axis relative to its orbit around the Sun. Our yearly calendar that we rely on is based on an equal length of days throughout the year.
The mean solar day (or time told by a watch or clock), calculated by averaging all the days of the year, was invented by astronomers for
convenience, so that the solar day would always be 24 hours. The true solar time and mean solar time coincide four times a year, April 16, June 14, September 1 and December 25. On these days, the Equation will equal zero.
During the other 361 days, the equation of time must be used to indicate the difference between the two times, amounting to about 16 minutes at certain times of the year.
The minimum difference occurs on November 1, with a loss of 16 minutes and 23 seconds; and the maximum occurs on February 11 with an increase of fourteen minutes and 20 seconds.
These positive and negative values are the offset in the time of the local noon and those of sunrise and sunset. The equation of time is often represented by a figure 8, calied an “analemma”.
The equation of time can be approximated by the following formula:
E = 9,87 × sin(2B) - 7,53 × cos(B) - 1,5 × sin(B) Where B = 360 × (N-81) / 365 Where N = day number, January 1 = day 1.
