In the Neuchâtel Jura, making white gold ring is a matter of elementary physical contradiction. The metal is dense, heavy, quick to smother sound waves. For a chime to cross a case middle without dying within it, traditional watchmaking demands volume, air, a generous echo chamber. The ultra-thin watch demands the exact opposite: driving out empty space, crushing tolerances, compressing the gear train to a tenth of a millimetre.
In La Côte-aux-Fées, the automatic calibre 1290P chooses precisely this zone of discomfort. Its 430 components are arranged within a case thickness held to 9.3 millimetres for a 48-millimetre diameter. The acoustic equation is solved here not by space, but by the tension of the materials and the geometry of the gongs. The calibre develops 64 decibels and maintains a damping factor measured at 2,600: the impact of the mirror-polished steel hammer produces a clear wave, supported by three precise harmonics. The hours chime on G sharp, the minutes on A sharp, both set in the fifth octave.
The movement hides nothing of its inertia. On the dial side, a cut-out in the hand-guilloché sunray-pattern gold dial opens a view onto the mechanism of cadence. At four o’clock, beneath a smoked blue sapphire ring engraved with the name of the Maison’s birthplace, the inertia wheel turns in the open air to regulate the cadence of the chime. It replaces the old lever escapement with a silent governor: no parasitic click disturbs the note.
To wind the mechanism without distorting the curved profile characteristic of the Polo line, the trigger control is placed at nine o’clock in the form of an inverted slide operating from top to bottom. Water resistance remains guaranteed to 30 metres, a rare feature for a minute repeater, whose acoustic openings ordinarily weaken watertightness. Automatic winding is provided by a platinum micro-rotor treated with blue PVD, whose density compensates for the small radius of oscillation.
Each dial requires one hundred and fifty hours of manual cutting, to which are added fifty hours of adjusting and bevelling the bridges. An economy of gesture that tolerates no correction: within 9.3 millimetres of thickness, the slightest burr of metal smothers the note before it reaches the case.
Detail Inertia governor at 4 o’clock: visible beneath its blue sapphire disc, this centrifugal governor dissipates the energy of the chiming barrel without emitting the mechanical hum typical of conventional friction governors, preserving the purity of the fifth octave.
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