Timekeepers Club / June 26, 2023

Armin Strom Pure Resonance Ultimate Sapphire "Horomariobro"

Pure Resonance Ultimate Sapphire: a unique collaboration between Armin Strom and influential watch collector Horomariobro becomes a limited edition.

The creative and renowned watch collector Horomariobro, dubbed “the King of Macro photography” on Instagram had the desire for Armin Strom to create a unique piece. The result – the Pure Resonance Ultimate Sapphire with a sapphire dial, a unique highly symmetrical design with exquisite hand decorations – turned out so visually striking that it was decided to share it with an exclusive few. Ten pieces will be available exclusively through Oster Jewelers in Denver, USA, who was also involved in this special collaboration.

I always loved the idea of having an Armin Strom Resonance timepiece in my collection,” said US West Coast-based watch collector known as @horomariobro on Instagram, who dives deep into haute horlogerie details with his camera. His near-microscopic approach separates the wheat from the chaff when it comes to haute horlogerie finishes and has given him a revered position among collectors, not to mention tens of thousands of followers on Instagram.

It has also made him a long-time friend of Armin Strom’s retail partner Oster Jewelers in Denver, a pioneering and passionate force for independent watchmaking brands like Armin Strom. Said founder Jeremy Oster: “After a series of conversations with @horomariobro, I reached out to Claude at Armin Strom, and together the three of us created the Pure Resonance Ultimate Sapphire – a sophisticated dream watch.”

It was a very organic and creative collaboration, and sometimes you need a push from the outside to make radical changes that you wouldn’t dare to think about yourself, like removing the seconds,” added Armin Strom’s co-founder and master watchmaker Claude Greisler about the monochrome, highly technical timepiece with an extreme level of hand-made haute horlogerie decorations. “The end result was so nice that together, we decided to make a limited edition of 10 pieces.

The 42-millimetre steel-cased Pure Resonance Ultimate Sapphire is the most minimalistic resonance timepiece made in Armin Strom’s fully integrated manufacture in Biel/Bienne. To fulfil Horomariobro’s wishes a sapphire dial has been applied, and the small seconds as well as Armin Strom’s historical lip on the case at 6 o’clock, have been removed. Even the logo is omitted, albeit for a subtle AS symbol engraved on a movement component. These radical reductions enhance the overall symmetry and highlights Armin Strom’s extreme in-house abilities for movement production and haute horlogerie decorations. Furthermore, the less-is-more approach enhances the kinetic marvel of the resonance clutch spring connecting the two balance wheels oscillating in resonance towards and away from each other.

I always loved Armin Strom’s resonance approach from both a physics and a mechanical point of view,” said Horomariobro about the patented invention for improved precision and chronometric stability, developed by Greisler and his team. This is not only visually intriguing, but has also become a watch industry benchmark, as it delivers the fastest, best-performing and most shock-resistant resonance solution in the world.

When it comes to the hand-made decorations on the Pure Resonance Ultimate Sapphire, Armin Strom created a unique combination. The black PVD-coated gear train bridges are adorned with a unique grain d’orge guilloché pattern by Kari Voutilainen, whereas all other decorations are made in-house by Armin Strom. Edges are hand-bevelled wherever humanly possible, the balance bridges are skeletonised and circular grained, other bridges are hand frosted, mirror polished, or perlaged. And note the grainy texture on the winding bridge on the right: an exquisite example of tremblage achieved by one of Armin Strom’s master engravers spending hours and hours carefully and painstakingly digging a frosted pattern with a customised engraving tool.

The open-worked backside has undergone a significant technical development, showing off the crown wheel’s improved ratchet mechanism (which gives the click-click sound when you wind the watch). The backside also carries “the pin”, Armin Strom’s seal of origin. This has been engraved with “Horomariobro”, the Armin Strom symbol and a unique serial number in the limited edition, before being matt finished, hand-bevelled and circular-grained.

I never expected my simple request for a unique piece would turn into a limited edition with my IG name on it. This collaboration with Claude and Jeremy makes me very proud and honoured – it’s definitely a milestone in my watch-collecting journey,” said Horomariobro.

Technical specifications

Armin Strom Pure Resonance Ultimate Sapphire "Horomariobro" Edition

Reference: ST17-RP.SA

Limited edition of 10 pieces


  • Material: Stainless steel
  • Diameter: 42.00 mm
  • Height: 13 mm
  • Sapphire crystal and caseback with anti-reflective treatment
  • Water-resistant to 5 ATM

Dial and hands

  • Dial: Gray metallic sapphire dial ring
  • Hands: Manufactured by Armin Strom, steel with hand finishing and Super-LumiNova® filling


  • Armin Strom manufacture Calibre ARF16
  • Manual-winding, patented resonance clutch spring, 2 mainspring barrels
  • Regulating system: two independent regulation systems connected by a resonance clutch spring
  • Power reserve: 48 hours
  • Dimensions: 34.40 mm x 7.05mm
  • Frequency: 3.5 Hz (25,200 vph)
  • Finishing: Base plate and bridges are decorated to the highest quality level
  • Number of jewels: 38
  • Number of components: 213


  • Hours, minutes

Strap and buckle

  • Delivered with a black fabric strap with light grey stitching and stainless-steel double folding clasp

MSRP: USD 59'000

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