Arnold & Son Ultrathin Tourbillon Skeleton Watch Review
The Arnold & Son Ultrathin Tourbillon Skeleton delivers an unparalleled quotient of nakedness courtesy of its openworked torso, allowing the wearer to see the movement’s many thought processes in real-time. However, as Angus Davies explains, some of the model’s attributes necessitate an expert’s discerning eye to fully appreciate its notable brilliance.
Skeleton watches – understanding the mechanical mind
Humans have an innate curiosity, motivating them to seek knowledge. This quest for understanding can be seen in various fields, including watchmaking. For example, the skeleton watch eschews a dial, inviting its inquisitive wearer to explore the inner workings of its mechanical mind.
Dating back to the 18th century, the skeleton watch is designed to share its thoughts, helping the wearer understand the role of each component. However, despite this high quotient of openness, there are prerequisites for the reliable operation of a skeleton watch that many horophiles may not be aware of. I was reminded of this when I first saw Arnold & Son’s latest release, the Ultrathin Tourbillon Skeleton. This model is blessed with a prepossessing appearance and reveals a plethora of components usually located out of sight. However, this eminently handsome watch has many attributes that may go unnoticed by non-experts. Allow me to elaborate.
Arnold & Son UTTE (Ultra-Thin Tourbillon Escapement) first released in 2013
The new Arnold & Son Ultrathin Tourbillon Skeleton is not the brand’s first foray into making tourbillons or tourbillon skeletons. On the contrary, the Maison has an impressive track record of making ultra-refined watches that compete in these market segments. For this reason, before discussing this latest creation, I feel it is necessary to provide some ‘UTTE’ history.
In 2013, Arnold & Son released the UTTE (Ultra-Thin Tourbillon Escapement). The watch was equipped with Breguet’s gravity-negating mechanism and featured an off-centre hour and minutes display positioned in the upper region of the dial.
The model was endowed with the Manufacture movement A&S8200, a hand-wound calibre equipped with twin barrels, delivering a prodigious power-reserve of 90 hours. And yet, despite the model’s capacity to store vast amounts of energy, it was still modestly sized, measuring 42 mm in diameter and just 8.34 mm in height. Over the years, the Manufacture based in La Chaux-de-Fonds has released several additional variants of the UTTE and incorporated an array of changes.
For example, at Watches & Wonders 2023, Arnold & Son unveiled the Ultrathin Tourbillon Gold & Opal Dial. Unlike the 2013 model fitted with an index-regulated balance, last year’s release was endowed with the A&S8300 calibre featuring a technically superior means of regulation, the variable-inertia balance. I could cite additional improvements found on the most recent UTTE models, but there are more pertinent matters to discuss. Save to say, the Maison’s continuous pursuit of product advancement is much in evidence.
Arnold & Son UTTE Skeleton first released in 2016
Three years after releasing the inaugural UTTE model, Arnold & Son unveiled a skeleton version of the watch. The UTTE Skeleton shared the same dimensions as its older sibling. It also featured the same A&S8200 calibre endowed with a one-minute flying tourbillon and, once again, it was equipped with twin barrels.
Images – Arnold & Son UTTE Skeleton 2016
As you would expect with this watch, based on its name, it was openworked and lacked a conventional dial. However, Arnold & Son took the notion of skeletonisation to a whole new level. There were few parts of the movement that remained hidden from view. Indeed, the naked mainplate had been pared back to form a complex labyrinth of highly decorated grey NAC-coated German silver. When held aloft, the watch’s movement exhibited a near-diaphanous quality, allowing light to pass through its exposed, intricately formed torso.
Images – Arnold & Son A&S8200 calibre
Now, there is a new UTTE Skeleton or, as the brand likes to say these days, an ‘Ultrathin Tourbillon Skeleton’. Similar to the ‘regular’ Ultrathin Tourbillon, the latest Ultrathin Tourbillon Skeleton resembles its forebears but also incorporates several product improvements.
Arnold & Son Ultrathin Tourbillon Skeleton – dimensions
The Arnold & Son Ultrathin Tourbillon Skeleton is a smidgen narrower than the 2016 release, measuring 41.5 mm (previously 42.0 mm), and a tad thicker at 8.40 mm (formerly 8.34 mm). However, it is unlikely that you will discern any difference in size. Some of my fellow ‘geeks’ may spot the design of the lugs has slightly changed but otherwise, at this stage, everything appears virtually the same.
Arnold & Son Ultrathin Tourbillon Skeleton – red gold or platinum
Would-be wearers have a choice of case materials: red gold or platinum; each supplied with an optimally-hued strap. Personally, I prefer the platinum option, but then again I have a reputation for always selecting the costliest dish on a restaurant menu. Each reference is limited to just 28 pieces.
Arnold & Son Ultrathin Tourbillon Skeleton – front of house
The grey NAC treatment of yesteryear has been set aside in favour of rose gold PVD treatment (4N). This simple change imbues the composition with a warmer and more luxurious appearance. Likewise, the off-centre hour and minutes display is now framed with a white opal track, providing a greater degree of contrast against the adjacent mainplate. This seemingly simple change has significantly improved the dial’s legibility, a problem that often afflicts many skeleton watches. Furthermore, the brand has teamed blued hour and minute hands with Roman numerals to clearly impart meaning, a feat it has achieved with notable aplomb.
Arnold & Son has delivered a harmonious composition. The aperture for the tourbillon appears to share the same sized footprint as the hour and minutes display, conferring a becoming degree of balance. This stacked series of circlets resembles a figure of eight, a fact that won’t go unnoticed in some parts of the world.
Arnold & Son Ultrathin Tourbillon Skeleton – flying tourbillon
The ‘flying tourbillon’, a term used to describe a tourbillon supported solely from below, is different in appearance to that of the 2016 model. The cage is now an inverted v-shape which, in my opinion, looks more attractive. The absence of an upper bridge affords superior views of the balance, escape wheel and balance spring. These latter components, along with the cage, are in a constant state of motion, delivering a captivating spectacle.
Arnold & Son A&S8320 calibre
The movement components are presented in silver tones, hence they readily stand out from the adjacent golden hues of the mainplate and bridges. By optimising contrast, Arnold & Son has accentuated the presence of the moving parts, a spectacle that will undoubtedly appeal to mechanically inquisitive wearers.
The keyless works is exposed, affording sight of the winding stem, winding pinion, setting lever, etc. The gear train is located opposite, arranged along the right flank of the movement, while the barrels have partially openworked covers, revealing both mainsprings in various states of tension.
Cast your eyes to the aforementioned hour and minute display and you will see the motion works with the hour wheel located centre-stage. This watch will sate the desires of the most fervent horological voyeurs.
Like its UTTE antecedents, the A&S8320 calibre is hand-wound and features two barrels. However, the power-reserve on this latest movement has increased from 90 hours (2016 version) to 100 hours.
The balance has a frequency of 21,600 vph (3Hz) and the movement contains 29 jewels. As stated previously, this latest movement is fitted with a variable-inertia balance. Most movements feature an index-regulated balance. When a trained watchmaker moves the index or raquette, either towards or away from the stud, the effective length of the hairspring increases/decreases, altering the rate.
With a variable-inertia balance, the effective length of the hairspring remains constant. A watchmaker adjusts the position of the weights affixed to the balance wheel, altering the moment of inertia and thereby causing the movement to run faster or slower. By adopting this approach, the rate can be set more precisely and, should the watch be subjected to a shock, it is less likely to require remedial regulation.
Instead of using traditional timing screws, positioned on the rim of the balance wheel, Arnold & Son has used C-shaped weights, termed ‘masselottes’ and located them on the spokes of the balance wheel. By adopting this approach, the balance wheel generates less air turbulence as it oscillates, augmenting precision.
The Arnold & Son A&S8320 calibre is a wonderfully refined movement. The mainplate is adorned with Côtes de Genève rayonnates and the bridges are polished and chamfered by hand. Moreover, the wheels are ‘circular satin-finished’ and the screws are chamfered and feature polished heads. Viewing the movement through a loupe reveals the tourbillon cage is polished, satin-finished and chamfered. All of these finishes are expertly imparted by hand.
One of the topics that is seldom discussed by watch brands is torsional rigidity, perhaps following the lead from the automotive industry. Indeed, few car marques refer torsional rigidity when discussing cabriolets, subscribing to the ‘best not to mention’ approach. Likewise, when a watch brand creates a skeleton watch by removing sections of the mainplate, it can sometimes introduce an unwanted degree of floppiness. This was a particular issue with traditional skeletons where extraneous material was removed with a combination of handsaws and files, resulting in a pretty watch that lacked sufficient stiffness. This lack of rigidity can potentially impair reliability and precision.
Arnold & Son has designed the A&S8320 calibre using CAD, removing surplus metal while ensuring the jewel beds, pivots and other load-bearing sections are left virtually untouched. CAD can simulate the forces acting on each part of the movement to ensure that torsional rigidity is maintained. The mainplate and bridges on this watch are formed using modern techniques, including CNC where metal can be milled to tolerances measured in microns. By adopting said technology, Arnold & Son has been able to produce a skeleton movement free of compromise.
Arnold & Son Ultrathin Tourbillon Skeleton – closing remarks
The Arnold & Son Ultrathin Tourbillon Skeleton has a prepossessing appearance, blessed with sinuous curves and chiselled features. Its handsome mien is clear to see. Moreover, its thoughts are freely shared with the onlooker. The mainsprings relax over time as the gear train transmits power to the escapement. It’s a slow process that is barely perceptible to the naked eye when viewed in real-time. On the other hand, the escapement, regulating organ and tourbillon cage move with greater alacrity, performing a spellbinding dance that is immediately apparent.
However, it’s only when you look at this watch with the benefit of expert knowledge that you can truly appreciate its many complexities and notable brilliance. The flying tourbillon, twin barrels, variable-inertia balance and the torsional rigidity of the movement, distinguish this watch as extraordinary. Having revealed its many complexities and depths, I hope you will share my appreciation for this watch’s beautiful appearance and brilliant mind.
Further reading
Technical specification
- Model: Arnold & Son Ultrathin Tourbillon Skeleton – 18-carat (5N) red gold – 1UTBR.Z01A.C246R
- Model: Arnold & Son Ultrathin Tourbillon Skeleton – platinum – 1UTBX.Z01A.C245X
- Case: diameter 41.5 mm, height 8.40 mm, water resistance 3 ATM (30 m), sapphire crystal to the front and exhibition case back
- Functions: Hours, minutes
- Movement: A&S8320 calibre, hand-wound movement; frequency 21,600 vph (3 Hz), 29 jewels, power reserve 100 hours
- Strap – red gold: dark blue alligator strap, black alligator lining, hand-stitched, paired with a folding clasp in titanium with a cover in 18-carat (5N) red gold
- Strap – platinum: brown alligator strap, black alligator lining, hand-stitched, paired with a folding clasp in titanium with a cover in platinum
- Swiss retail price: – Platinum – CHF 74,400 including taxes (RRP as of 22.2.2024) – 28 timepieces
- Swiss retail price: – Red Gold – CHF 86,200 including taxes (RRP as of 22.2.2024) – 28 timepieces