Armin Strom's work with resonance has become one of the defining strands of the modern manufacture, beginning with the Mirrored Force Resonance in 2016 and its patented clutch spring connecting two independent regulators. The Pure Resonance Ultimate Sapphire takes that concept in a particularly focused direction. It originated as a unique commission from collector and macro-photography specialist Horomariobro, whose fascination with exposing the smallest details of movement construction informed the design. Armin Strom subsequently developed the concept into a limited edition of just ten pieces, available exclusively through Oster Jewelers in Denver.

The result strips the resonance watch back to its essential mechanics. Horomariobro requested the removal of the conventional twin seconds displays, the elimination of the characteristic case lip at six and, most significantly, a transparent sapphire hour-and-minute dial. This leaves the two synchronised balance wheels and patented resonance clutch spring unusually exposed, alongside black PVD-coated bridges decorated with a barleycorn guilloché pattern by Kari Voutilainen. Behind it sits the manually wound manufacture calibre ARF16, with two independent gear trains and mainspring barrels feeding the paired regulators. This example is individually numbered 5/10.