Horological Vocab: Important Terms Every Collector Should Know

Horological Vocab: Important Terms Every Collector Should Know


Talk the Talk

The world of timepieces – with its seemingly infinite list of moving parts and definitions – may seem intimidating to new collectors. But once you learn what makes watches tick, you’ll realise that becoming a confident buyer or seller isn’t all that complicated. Here is a list of key terms to help get you started, plus fine timepieces from the Important Watches I auction (5 October, Hong Kong) to provide helpful illustrations.



A small window that displays indications such as the date, day or moon phase.

Patek Philippe Nautilus, Reference 5726. Originally launched in 1976, the Nautilus has gone through many modifications while remaining an icon of Patek Philippe. The reference 5726 was first released in 2010 as an extension of the original Nautilus family and was the first stainless steel Patek creation to feature an annual calendar complication, with the day, date, month, and moon phase all displayed via apertures on the dial. Requiring calibration only once a year, this effortlessly stylish timepiece is the product of legendary design and expert watchmaking execution.

The Important Watches I auction includes multiple significant examples of this reference, including an extraordinarily rare model featuring the prestigious logo of Tiffany & Co. stamped on its smoky grey, horizontally embossed dial. Notably, this uncommon detail is only acquired from Tiffany’s New York boutiques by very important clients, with it often considered one of the most desirable double signatures to have on a timepiece besides the original manufactures.

The auction also includes an example of the most recent iteration of the reference 5726, with the updated design introduced in 2019. This example pays homage to the original Nautilus with its elegant blue-black graduated dial with telltale horizontal embossing. While the stainless steel case conceals the impressive annual calendar, the wearer can always admire the mechanics through the sapphire crystal case back. A marriage between advanced watchmaking artistry and legendary design, this timepiece is undisputedly powerful and effortlessly stylish.

Balance Wheel

A weighted wheel that regulates the pulses of a watch or chronometer by rotating back and forth, driven from impulses delivered by the escapement.

Philippe Dufour Simplicity, Number 167. While technology has given many manufacturers the ease and ability to produce in large quantities, Philippe Dufour prioritises traditional watchmaking craftmanship and technique, hand finishing every component of his creations.

Introduced in 2000, the Simplicity was debuted to cater to legendary watchmaker Philip Dufour’s large and devoted following in Japan. Though the seemingly minimalist timepiece only shows time, the Simplicity is prided on being a product of the utmost quality, with this 2011-made example showcasing just that. With inspiration from traditional Vallée de Joux movements, Dufour makes use of traditional techniques in his craft and hand finishes each component to perfection, never to exclude subtle details such as the instantly recognisable Geneva stripes seen on the movement or the high polish on the balance wheel contained within it.


The forward-facing top ring surrounding the dial, usually referring to the outer bezel, or the top part of the case.

Patek Philippe, Reference 5339. The brilliant combination of tourbillon and minute repeater was first produced by Patek Philippe in 1993 with the reference 3939, with it now being considered one of the manufacturer’s greatest grand complications. The present reference 5339 model is the successor of the iconic reference and was produced solely in pink gold from 2010. Its production period was very short and only a few dozen pieces were made in total.

While possessing some features similar to its predecessor – such as the skillfully made white enamel dial – seen on this model is a slightly larger pink gold case with a quintessentially Patek Philippe Clou de Paris bezel. This intricately guilloched hobnail pattern bezel was first seen in 1932 and often features on Calatrava models, though rarely seen on Grand Complications. These subtle but distinct details together with the contemporary baton numerals make this timepiece a picture of understated elegance and highly attractive.


Known as the body of the watch, the case contains all its inner workings and gears.

Cartier Crash, Reference 2463. Designed by Jean-Jacques Cartier in 1967, the Cartier Crash is more than just an iconic watch, it became an emblem for post war spirits, the swinging sixties in London, and new unprecedented times in culture and society.

While the Crash has and is best known for its signature asymmetric case, it still manages to look completely balanced and has a dial that is easy to read. Produced in very limited numbers, the current lot features a rare pink gold case that beautifully complements the Cartier classic sapphire cabochon crown. Highly sought after, the only contemporary Crash for retail is found in the London Bond Street boutique, where one gold Cartier Crash is available per month. A symbol of Cartier and a revolutionary period of history, this rare and highly coveted timepiece would make a wonderful addition to any collection.

Retrograde Date

A distinct manner of displaying the date on a dial, usually via an analog partial-circle with the indicating hand snapping back to “1” after completion of the previous month.


Patek Philippe, Reference 5016. Considered by collectors to be one of the greatest classical complication watches produced by Patek Philippe, the reference 5016 was the brand's most complicated watch ever produced, until surpassed by the Sky Moon in 2001. It inherits a similar case design from the reference 2499, and within a case of only 36mm incorporates three of the most complicated watchmaking functions, including a tourbillon, perpetual calendar, and minute repeater. A fan shaped retrograde date balances the aesthetic and adds to its distinction.

Patek Philippe, Reference 5160. Positioned as the successor to the reference 5159, the reference 5160 launched in 2010 and is a masterclass of both hand-craft watchmaking artisanship and innovative modern technology. Immediately upon viewing, one’s quickly mesmerised by the utterly fine engravings throughout the dial and case, the details even extended to the screws and clasp.

Reminiscent to vintage pocket watches, this timepiece incorporates a hinged cuvette in an Officer style, with the magnificent automatic perpetual calendar movement revealed once opened. The calibre powers the operation of the silvered dial, complete with Breguet numerals and classic spearhead hands, which includes among its various calendar functions a suave retrograde date.


Casually referred to as the "face" or "front" of the watch, the dial displays the time among other possible information.

Rolex Cosmograph Daytona, Reference 116568BR. Originally designed to be the ultimate tool watch for racers, the Rolex Cosmograph Daytona has proved to stand the test of time, becoming one of the most recognisable watches in the world of horology. The current lot presents a luxurious yellow gold variant, featuring a champagne mother-of-pearl dial and bezel set with 24 brilliant baguette-cut diamonds. Paired with a matching yellow gold Oyster bracelet, these rarely seen design elements complement each other beautifully and accurately depict constant innovation and creativity of the legendary manufacturer. This tried-and-true timepiece is not only elevated with uniquely elegant features but is in pristine condition with the protective stickers still on. Rarely produced and even lesser seen on the market, the current lot presents the perfect opportunity to obtain this important Daytona.


When a dial, movement, or some other component of a timepiece is designed to showcase its structural and / or internal pieces, i.e. its skeleton.

Girard-Perregaux Minute Repeater Tri-Axial Tourbillon, Reference 99830. One of the oldest manufacturers still in operation in Switzerland today, Girard-Perregaux has been making fine watches since its formation in 1791. The Minute Repeater Tri-Axial Tourbillon is a product of two incredibly advanced and technically challenging complications, in combination with the full range of Girard-Perregaux’s artisan skill.

Rarely seen titanium in fine watchmaking, the metal is very difficult to work with due to its strength and toughness. In this instance, the quality craftsmanship of Girard-Perregaux results in a powerful and stylish titanium case that is light and comfortable. The low-density nature of titanium also allows for maximum auditory efficiency of the minute repeater complication, resulting in impeccably precise, powerful and harmonious chimes as the hammers strike. Also housed within the movement is a tourbillon spinning on three different axes at varying speeds, creating a maximum of points where flaws in equilibrium and imbalances can cancel each other out regardless of the watch’s position. Thanks to the semi-skeletonised dial, the intricate components of the minute repeater as well as the tourbillon cages can be appropriately admired. An aesthetic and mechanical statement, this impressive timepiece commands attention to its wearer’s wrist at the first glance.

Bovet Récital 26 Brainstorm Chapter One. Following the release of the three astronomical tourbillon watches, the Shooting Star in 2016, the Astérium in 2017, and the Grand Récital 22 in 2018, Bovet would finally present the Récital 26 Brainstorm Chapter One in 2019. Not only does it continue the rejuvenation of tourbillon watches for the brand, it also inherits in the inclined "writing desk" case just like the former trilogy.

The spectacular skeletonised architecture of the wristwatch is fully exhibited under the sapphire crystal case, showcasing the three-dimensional moon phases, big date, power reserve of ten days and of course, a flying tourbillon at 6 o'clock. Highlighting the incredible movement would be the centrepiece of the dial, manufactured from blue quartz. The feature not showcases the beauty of transparency, but further demonstrates the vision of Bovet's current owner Pascal Raffy as brilliantly delivered through this masterpiece.


Often referred to as the heartbeat within the watch, the escapement regulates timekeeping. While hundreds of different escapements have been modified and invented over the years, the most common modern version is the lever escapement.

Audemars Piguet Jules Audemars Chronometer with Audemars Piguet Escapement. While a majority of Swiss made watches utilise the conventional lever escapement, Audemars Piguet had the idea to invent a better escapement by themselves. The present lot features a direct impulse escapement which uses less energy compared to a traditional Swiss impulse lever. This allows for the escapement to run at 6Hz, 43,200 beats per hour opposed to the normal 3 or 4 Hz. Based on the construction, running a traditional escapement at 6Hz, would cause the lubricants to fly all over the place whereas the AP escapement allows less energy to accomplish higher vibrations. Altogether the movement gives higher accuracy and precision in timekeeping.

Apart from the technological side, the movement is incredibly well finished where the twin barrel is mirror polished with nice beveling on other parts as well, captured under the sapphire display back. On the front, the spacious case creates a 3-D view of the semi-skeletonised watch. A joy to look at, the balance wheel runs extremely fast below the black enamel dial, a technical timepiece not to be missed.


The watch’s hands point to the correct time or other information located on the dial.

Vacheron Constantin Mercator, Reference 43050. The collection of Vacheron Constantin Mercator pays homage to a legendary cartographer, Gerardus Mercator. His most well-known creation, the Mercator projection, is a geographical map that flattens the spherical globe into a 2-D map and uses a grid of straight latitude and longitude lines to represent location. Mercator's influence in geography dates back to the 16th century and his ideas are still being used today.

Celebrating Mercator's genius with a series of timepieces bearing champlevé enamel dial, master enamelers Lucie and Jean Genbrugge were the artisans behind the working bench for this model. More importantly is the map featured in the magnificent dial and its incredible pair of hands operating in a retrograde fashion. Featuring Hong Kong’s iconic Aqua Luna red sail junk boat, this limited edition of 30 watches was made to commemorate the handover of Hong Kong to China in 1997. Bearing the number 28 as engraved to the band, the present timepiece not only marks an historic event but showcasing the mastery of Swiss fine watchmaking.


Sometimes known as indices, these are markings (shapes, numbers, Roman numerals, etc.) that hands point to in order to tell time.

Patek Philippe, Reference 5539. Patek Philippe’s Grand Complication collection has its incredible depth including horological marvels from split seconds chronographs to renowned complications such as minute repeating and tourbillons. Often considered as grail watches, obtaining one of these watches from the legendary manufacturer is a dream for many connoisseurs.

The story of combining tourbillon and minute repeaters – namely two of the most important complications in horological history – started from the reference 3939 in 1993. At that time, the timepiece was a shock to the watch community, but it went on and became one of Patek Philippe’s most coveted lineages to date.

This reference, the 5539, saw its introduction in 2013, and marked a modernisation for the series. Notably the watch opts for the same movement RTO 27 PS as the 3939, though now housed in an enlarged officer-styled case. The black enamel dial further highlights the mastery of the maison, with the precise craftsmanship of the hour and minute indexes and their matching spade-style hands speaking loudly without any excessive flourish or noise. Only a handful of these watches have resurfaced to the market, and we are honoured to present a spectacular example, an one-of-a-kind opportunity not-to-be-missed.



In simplest terms: A complication is something a watch does. Individual complications can include chronographs, calendars, GMTs, and much more. If a watch has a combination of at least three different advanced functions, it’s referred to as a grand complication.

Patek Philippe, Sky Moon Tourbillon, Reference 5002. Being the world’s most complicated wristwatches at the time of its launch, the biggest challenge to the Sky Moon’s development was incorporating its movement of 694 parts into the small cavity of a wristwatch. Perfectly achieved by Patek Philippe, the 43.5mm case houses a tourbillon and a minute repeater with cathedral gongs, alongside the perpetual calendar with retrograde date remarkably displayed on the front dial. Turning to the back of the dial, a magnificent blue northern sky chart pops right in front of the eyes. Not only displaying angular progression and the phases of the moon, the sidereal time based on the Earth’s rotation is also shown with clarity. Under the sapphire case back, the canopy of the northern hemisphere rotates counterclockwise with the passage of time, showcasing the celestial motions. The astronomical highlight adds a level of romance to the watch and pays homage to the origin and quintessence of timekeeping. Combining the level of accuracy between the two sides of the movement, its sophistication would require many months to complete and is embossed by the Geneva Seal, just like all other Patek Philippe tourbillon pieces from this era.


A day-date complication indicates both the day of the week and the date of the month. The triple calendar further elaborates upon the day-date, by indicating the month, while an annual calendar also accounts for the varying length of months. A perpetual calendar is even more sophisticated by automatically adjusting for leap years.

Patek Philippe Nautilus, Reference 5740. Originally launched in 1976, the Nautilus has become the epitome of a luxury sports watch and an icon of the Patek Philippe brand. Initially only produced in steel, as the demand for the Nautilus expanded, so did the production of the Nautilus family to include precious metals and two-tone models in the 1980s. Further elevating this classic collection, the reference 5740 model launched in 2018 features a perpetual calendar, making it the first Grand Complication Nautilus collection.


A chronograph is essentially a stopwatch that has the ability to measure time or an event. Within chronographs there are different variations, including the split-seconds chronograph, which can time two things simultaneously.

A. Lange & Söhne Datograph Up/Down "Lumen", Reference 405.034. The Datograph Up/Down collection is part of the Saxonia watch family, which saw its debut in 1994 along with the rebirth of A. Lange & Söhne. Whilst the focus of a Saxonia is to find an optimal mechanical solution, the ease of readability and functionality provided by a mechanical chronograph combined to create an amalgamation of ingenuity and elegance.

What is even more intriguing is that the current example set for sale is a part of the “Lumen” series launched by the German powerhouse in 2010, making this modern classic even more desirable than it already was. This impressive timepiece released in 2018 is simply mind-blowing with its semi-transparent sapphire crystal dial which glows in dark displays. Thanks to luminous pigments powered by natural light coating the central hands, power reserve indicator and outsize date display housed within a fine platinum case, the distinctive design elements of the watch become literally dazzling.

Digital Display

Displays the time in the form of digits rather than by hands on a dial.

A. Lange & Söhne Zeitwerk Date, Reference 148.038. Introduced in 2009, the present watch is an example of mechanical ingenuity. The Zeitwerk is the first mechanical wristwatch that displays time digitally with a jumping numerals mechanism seen in the time bridge, which is framed by rhodium German silver. Though the beautiful display is immediately understandable, the inner mechanics of this timepiece are groundbreaking and will leave the wearer with much to explore. The Zeitwerk is also unique in that its design differs from the traditional form of other A. Lange & Söhne timepieces, making this award-winning watch a truly innovative masterpiece.

In commemoration of the 10th anniversary of the Zeitwerk, the present Zeitwerk Date was released in 2019 and features an enhanced date indication. The addition of another date window would disturb the balance of the dial, so to work around this, the ingenious minds of A. Lange & Söhne's watchmakers designed the date to be on the exterior rim of the dial, indicating the date in red.

Moon Phase

The moon phase complication gives you a visual representation of phases of the lunar cycle, either in a picture or in days.

Patek Philippe Celestial, Reference 5102. A beautiful combination of the Swiss manufacture’s technical prowess and artisan skill, the Celestial is a captivating and highly complex timepiece that highlights Patek Philippe’s longstanding legacy of producing astronomical watches. First produced in 2002, the intricate sky canopy of the celestial reference 5102 mirrors the reverse dial of the Sky Moon Tourbillon reference 5002, one of the most complicated wristwatches produced by the manufacturer, featuring 12 different horological complications.

The rich blue dial adorned with shimmering gold stars illustrates the nocturnal sky of the northern hemisphere with an elliptical aperture that frames the portion of the sky visible from Geneva at any time, displaying an impressive range of astronomical complications including a sky chart, moon phase and positioning, and the time of meridian passage of Sirius and the moon.The current example featuring a platinum and pink gold case was released in 2009 and discontinued in 2012 after a very limited production, making this visual and mechanical masterpiece a highly collectable and unique timepiece.

Power Reserve Indicator

One popular complication is the power reserve indicator, which tells the wearer how long a watch will last or keep going before it needs to be wound.

F.P. Journe Octa Réserve de Marche. The Octa collection embodies the original legacy of F. P. Journe's automatic watches. In fact, even today, F. P. Journe would still be using the same calibre he developed back in 2001. Developed with longevity in mind, the calibre 1300 features an off-centered rotor to reserve space for future complications to be incorporated, which turned into reality down the line.

The present example is from F. P. Journe's very first attempt at an automatic watch: the Octa Réserve de Marche. The platinum watch features an incredible yellow gold dial executed in F. P. Journe’s signature aesthetic, with running time on side of the display, a large power reserve indicator in parallel, and a small date window above them both to balance the style.

Notably, this example features a movement crafted in rhodium plated brass – an extremely desirable trait from collectors. As a young brand, F. P. Journe would control their budget by employing the use of brass as a movement material until approximately 2004, then phasing out brass and favouring the use of pink gold as a movement material. These brass movement watches are now deemed extremely collectible as it represents the earliest heritage of the brand. According to research, no more than approximately 530 brass movements of the Octa Réserve de Marche were produced. The present example is cased in platinum with a yellow gold dial and preserved in excellent overall condition.


A repeater is a watch that can chime the time. There are different variations, including minute repeaters that strike different tones for hours, quarters and minutes.

Patek Philippe, Reference 5033. Patek Philippe produced their first minute repeating wristwatch in 1924 with sophisticated craftsmanship. Never failed to impress, the sound quality of a Patek Philippe repeater is astonishingly well made where the tone and clarity that it gave were unheard of, establishing their top reputation in the horology world. In addition, Patek Philippe incorporated a mind-blowing innovation in the early 2000s, via the "Cathedral" repeating mechanism, which consists of a high-tone and a low-tone gong where the length of the gong almost doubles the length of a regular gong. The result is a much richer and timbre sound, resembling the chime of the bells of a cathedral. Given the physical constraints of a small wristwatch, all the parts in the movement are perfectly in place as the slightest mis-position would lead to long hours of fine tuning.

The reference 5033 originates as a custom order of 10 platinum pieces and a unique titanium example in 2002. The cushion-shaped masterpiece is the first to combine their patented annual calendar with a minute repeater. Whilst the majority of the pieces were made with applied drop indexes, dials with roman numerals are very rare and only a handful have come back to the market. With only about 80 pieces made in total throughout the production span, the present lot not only features a super unusual black dial with Roman numerals, it also makes use of the “Cathedral gongs” that gives a subliminal chime upon activating the slider. With rarity and historical significance, the lot represents a perfect opportunity for collectors of minute repeating wristwatches to acquire such an incredible timepiece.


The tourbillon is a special type of escapement that rotates on an axis in order to counteract the effects of gravity and thus improve accuracy in a mechanical watch. A feat to be made, it’s considered a calling card of high horology.

Vacheron Constantin Malte Tourbillon, Reference 30672. Drawing its inspiration from the Art Deco period, the Malte collection places an emphasis on the appearance of the beauty of curves – holding itself distinctive among Vacheron Constantin's collection for its tonneau shape.

The Malte Tourbillon is an enhanced variation of the collection, seeing its initial launch in 2000 as a celebration of the millennium and stepping forward of the brand. Offered in various case material and creative configurations, the present example has a very rare setting fully skeletonised with enhanced baguette-cut sapphires on the bezel and pavé-set diamonds exhibited on the case band. Upon close inspection, one would notice the symbol of Vacheron Constantin's Malte cross would be ingeniously incorporated on the tourbillon carriage, rotating gloriously in one minute intervals. The present example has a unique configuration and is only offered to the most exclusive clients of Vacheron Constantin.



The movement, also known as the calibre, is what’s inside a watch and makes it run. There are many movements that employ proprietary innovations, but most movements can now be categorised as either quartz or mechanical.

F.P. Journe Tourbillon Souverain. Arguably one of the most influential and respected watchmakers of the era, François-Paul Journe manifested a combination of horological knowledge, innate talent and creativity, as well as modern technology to create distinct and unique masterpieces. The very first 20 F.P. Journe Tourbillon Souverain created in 1999 were Souscription models, where trusted clients received a 50 percent discount for the watch, allowing him to fundraise for his future masterpieces like this current piece. The Tourbillon Remontoir d’Egalite is one of F.P. Journe’s signature complications and is the first ever tourbillon wristwatch to feature a remontoire mechanism in its movement, enhancing accuracy by exerting a constant and equal amount of energy to the tourbillon.

The rarity of F.P. Journe’s tourbillon watches cannot be emphasised without mentioning the exceptional limited ruthenium collection which consisted of five models, each was limited to a scarce production of 99 watches. What is special and differentiates from other first generation Tourbillon Remontoir d’ Egalite watches are the 40mm case diameter and ruthenium finishing towards the dial and movement. Whilst they symbolised the end of the brass movement era, the timepiece represented the historic transition and remained highly sought after by collectors and enthusiasts worldwide.


Quartz watches utilize a battery or capacitor to charge and run the watch.

Piaget, Reference 77280. Piaget is one of the top producers of jewellery watches today. Georges Piaget founded the company in 1874 when he was just 19 years old. The current reference 77280 is a stunning example of the Maison's work, with a case and bracelet made of substantial 18k white gold, and a quartz-powered calibre 7P3 driving its timekeeping. The watch is interestingly set with a spectacular range of precious stones, including diamonds and sapphires, which work well in complementing the white gold presentation.


A manual-winding, or hand-wound watch is a type of mechanical timepiece that runs without batteries and is powered by winding the crown, which connects to the mainspring.

A. Lange & Söhne Datograph Perpetual, Reference 410.025. Introduced at an international trade show in 2006, the Datograph Perpetual is part of the Saxonia watch family that was launched in 1994 along with the rebirth of the A. Lange & Söhne brand. Although chronographs and their movements have been flagship products of the firm since their rebirth, this is the first A. Lange & Söhne creation to marry the well-loved flyback chronograph and perpetual calendar.

Encased in noble platinum, this timepiece is impressive in size as well as mechanics, all while still being comfortable to wear on the wrist due to the design of the protruding case back. The sapphire crystal display case back also reveals the magnificent manual-winding calibre L952.1 and enables wearers to admire the three-dimensional construction and intricate hand finished components of the in-house engineered movement. Also featured on the platinum case is a safety pusher at 10 o’clock that allows users to advance all calendar indications by one increment, only when the crown is pulled. Rarely seen in the market, the reference 410.025 had a short production span of five years, before a second generation Datograph Perpetual was introduced in pink and white gold, making this incredible timepiece a notable addition to any collection.


An automatic movement is type of mechanical movement that is wound by the oscillating weight (known as a rotor) inside the watch that moves in unison with the wearer’s wrist.

Richard Mille Reference RM67-02 “Wayde van Niekerk.” With the launch of the RM 67-02 collection in 2015 in titanium and then in carbon composite in 2017, Richard Mille presented to the market an incredibly lightweight sports watch achieving incredible technical sophistication and doing so using ground-breaking mechanical and material innovations. Specifically developed for optimum comfort and dynamic lines, the watch is made in a combination of ultra-special materials that weighs a mind-blowing 32 grams, making it the lightest automatic watch from the brand.

This edition of the RM 67-02 was made for South African sprinter Wayde van Niekerk who is an uncontested 400m Olympic champion and world record holder in 2016. The bezel and caseback having a remarkable damascene appearance are made in yellow and green Quartz TPT and the band is made in green Carbon TPT. Together with the hand-painted bridges, it not only resembles the colours of the South African flag but emits incredible aesthetics that distinguishes itself from other pieces in the collection.

Watches Hong Kong Autumn Auctions

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