In the late 1940s and 1950s, aerodynamic principles were just beginning to take root in automotive design. Curvilinear forms became more prominent, carrying the immediate promise of power and speed - but designers were guided more by their aesthetic sense than by any scientific precepts. Inspired by the dynamic profiles of automotive and aviation mid-century design, HM9 Flow treads the path first opened by the HM4 Thunderbolt and HM6 Space Pirate, utilising a geometrically complex combination of milled sapphire crystal and titanium or red gold case elements. But HM9 goes beyond its predecessors, redefining what was thought to be possible in case design. Reminiscent of a jet engine, the highly complex case encloses an equally complex manual winding movement, developed fully in-house. Twin balance wheels beat independently on each flank of the Machine, while the central body reveals the gearbox of the HM9 engine: a planetary differential that averages the output of both balances to provide one stable reading of the time. CASE Grade 5 titanium: 'Air' edition with aviation-style dial and NAC-finish movement / 'Road' edition with speedometer dial and red gold-finished movement 18k 5N+ red gold: 'Air' edition with aviation-style dial and NAC-finish movement / 'Road' edition with speedometer dial and rhodium-plated movement Dimensions: 57 x 47 x 23 mm 43 components (titanium), 49 components (red gold) Water resistance: 3ATM (30m); assembled in three segments with patented three-dimensional gasket. ENGINE Manual-winding in-house movement Two fully independent balance wheels with planetary differential Hours and minutes on vertical dial display Frequency: 2.5Hz / 18,000bph 301 components / 52 jewels / 45h power reserve. SAPPHIRE CRYSTALS Five sapphire crystals treated with anti-reflective coating.