Arnold & Son HM Double Hemisphere Perpetual Moon

Escapement’s contributing author, Carl Eady, reviews the stunning Arnold & Son HM Double Hemisphere Perpetual Moon and delves into the horological significance of English watchmaker John Arnold.

Arnold & Son HM Double Hemisphere Perpetual Moon


Inspired by the historical genius of British watchmaker John Arnold, the brand Arnold & Son has been making exceptional timepieces in La Chaux-de-Fonds since 1995. John Arnold was born in Cornwall in 1736. He was the son of a clockmaker and served his apprenticeship with his father before leaving England for Holland in 1755. In two industrious years working as a watchmaker in The Hague, Arnold became fluent in German. After his return to England he established his own watchmaking business, based in the narrow streets of Deveraux Court behind The Strand in London.

Given that King George III was Hanoverian, Arnold’s linguistic prowess, coupled with his horological aptitude saw him gain favour with the king and wealthy clients associated with the royal court. His inventive nature also saw him hold a series of watchmaking patents, including the detent escapement, bi-metallic balance, overcoil balance spring and helical balance spring.

In 1778, the introduction of his No. 36 pocket watch led Arnold to introduce the term ‘Chronometer’, used to describe a highly accurate timekeeper. His notoriety saw him play a key role in solving the nautical problem of determining longitude and, as a consequence, numerous seafaring captains utilised his Marine Chronometers on their far-reaching voyages.

His friendship with Abraham Louis Breguet is well documented, with the pair often sharing trade secrets. In addition, Breguet sent his son to Arnold in order to undertake an apprenticeship and likewise Arnold sent his son, the legendary John Roger Arnold, to Breguet for instruction. Such was the bond and respect between the two, after Arnold’s death, Breguet fitted the first ever tourbillon into an Arnold No. 11 movement in honour of their collaboration in developing this most innovative complication. Fittingly, Breguet presented this tribute to his former apprentice and John Arnold’s son, John Roger Arnold, who assumed control of his father’s business until his own death in 1843.

The brand was relaunched by a group of private investors in 1995 and has since set about producing timepieces encompassing the exalted techniques synonymous with haute horlogerie, upholding the legendary name of Arnold.

The HM Double Hemisphere Perpetual Moon is a gorgeously decorative timepiece, presenting two enormous moons which contrast against a stunning blue backdrop, while simultaneously depicting the moon phases in the northern and southern Hemispheres. Launched in 2016, the watch is a worthy member of the brand’s Royal Collection and honours a time when British watchmaking was unrivalled and Arnold’s mastery was revered by the Royal Court.


Being a direct descendent of the HM Perpetual Moon collection, which was unveiled to much acclaim in 2013, the dial on the Double Hemisphere has thankfully inherited many of its older sibling’s decorative characteristics. A guilloche ‘sunray’ pattern radiates from the centre of the translucent cobalt blue dial, exhibiting a playful vibrancy as light catches each ripple. Contrasting gold accents add a luxurious touch to the dial, reinforcing its regal credentials.

The faceted hour-markers are simple yet elegant, while the minutes are marked by unassuming gold dots – deliberate understatements so as not to detract from the watch’s cardinal feature. At 3 o’clock, arrows on a golden globe indicate the northern and southern hemispheres, adding a nautical tone, perhaps in subtle recognition of Arnolds maritime contributions. The bold gold hands retain the familiar form presented across the collection with a faceted sword shape reminiscent of the nib of a fountain pen.

Arnold & Son HM Double Hemisphere Perpetual Moon

Two large gold rimmed apertures shaped like manta rays frame the rotating disc within. Fashioned in the same ‘sunray’ guilloché pattern, the 29mm disc is dominated by two gigantic golden moons, each measuring 11.2mm. In order to depict the three-dimensional form of the moons, hand engraved ‘masters’ were created to provide a stunning blueprint, which thereafter could be duplicated for the brand’s lunar collection. The breathtaking result is a celestial celebration of the moon’s surface and its fascinating craters.


Many brands exhibit the phases of the moon but do so rather timidly through tiny apertures. Conversely, Arnold & Son has bravely opted to portray this gorgeous complication in expansive form, without compromising the watches classical styling.


Fashioned from 18-carat red gold, the circular case carries a slender stepped bezel. Its long elegant lugs are also ‘stepped’ with a highly polished base sitting adjacent to the satin brushed upper plane. At their tips, the lugs are shaped into an ornate curve. Lug to lug, the watch is 48mm, with the diameter measuring a substantial 42mm.  Due to the positioning of the spring bar in the lugs, however, the watch fits comfortably even on a smaller wrist.

Arnold & Son HM Double Hemisphere Perpetual Moon

Hours and minutes are set via a simple but sharply fluted crown that is detailed with the brands ‘Crown and Anchor’ logo, whilst a recessed pusher at the 2 o’clock position enables the moon phase setting.

When a dial proves as exquisite as Arnold & Son’s guilloché and moon phase combination, nothing should compromise the view. Thankfully, Arnold & Son has respected the splendour of the dial by applying an anti-reflective coating to both sides of the sapphire crystal. On the reverse of the watch, the decorative A&S1512 calibre is showcased via a screw down exhibition case back. The remainder of the red gold case is exceptionally polished and accentuates the timepiece’s luxurious composition.


Since the brands resurgence back in 1995, it has introduced numerous exceptional calibers. It is evident from the quality of finishing and invention that the brand manufactures watches without compromise, always doing justice to the legendary British watchmaker’s name. Powering the HM Moon collection is the caliber A&S1512. It is one of the most accurate moon phase watches on the market, necessitating just a single push of the case band corrector every 122 years. Through the exhibition case back, a third (eight phase) moon display is visible, allowing precise setting of the complication using a gold pointer.


Beating at 21,600 vibrations per hour, the hand-wound movement delivers a respectable 90 hours of power between winds thanks to its twin barrels. Whilst the construction of the 27-jewel movement is commendable, it is the hand finished decoration which will set owner’s pulses racing. Finished in rhodium treated nickel-silver, the movement’s bridges are manually chamfered and polished. Perlage is visible on the baseplate, while each wheel features fine circular graining and all components are secured with heat blued screws.  Dominating the look of the A&S1512 are Côtes de Genève rayonnantes which  emanate from the balance cock. This motif sits in perfect harmony with the rest of this horological masterpiece.



The classical features of the watch are complemented by a sumptuous hand-crafted brown alligator strap. Inside, the strap has a calf skin inlay embossed with the Arnold & Son logo. It is secured with a simple gold pin buckle. The space between the lugs is 20mm, so owners with a bent for personalisation will have numerous ‘after-market’ choices. The brand offers an alternative black strap option, though purists are likely to opt for the recommended chocolate brown choice.

Closing thoughts

If John Arnold and his son John Roger were alive today one suspects that they would be overwhelmed by the painstaking efforts today’s brand has gone to in order to keep their name alive. The Arnold & Son HM Double Hemisphere Perpetual Moon is a visually striking timepiece, combining a technically excellent movement with hand finished decoration of the very highest order. The interpretations of the moon surface are a work of art and, by virtue of their sheer scale alone, do justice to the complication. By presenting the moons against the vibrant blue guilloché backdrop, the brand has captured the decorative and horological spirit of John Arnold and his son, John Roger Arnold, two venerated historical figures from the esoteric world of high-end watchmaking.

Further reading

Technical specifications

  • Model: Arnold & Son HM Double Hemisphere Perpetual Moon
  • Reference: U03A.C122A
  • Case: 18-carat red gold; diameter 42mm; water resistance 3ATM (30 metres)
  • Functions: Hours; Minutes; Double Hemisphere Moon Phase; third Moon Phase indication on the reverse for setting purposes
  • Movement: Calibre A&S1512; frequency 21,600 VpH (3Hz); 27 jewels; power-reserve 90 hours.
  • Strap: Hand-stitched brown alligator leather with gold pin and buckle
  • Price: £26,400 (RRP as at 10.8.2019)


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