Each year Baume & Mercier offers an exclusive timepiece as part of the Clifton Collection, reflecting Baume & Mercier’s continuing commitment to building its collection of emblematic timepieces. The new Clifton Manual 1830 with TwinSpir technology is the latest edition to enrich the Clifton Collection — a collection already composed of remarkable watches including the Flying Tourbillon, the Perpetual Calendar or the 5-minute Repeater. This emblematic piece perfectly expresses the brand’s legacy. An 18K red gold case timepiece combining a number of specific design features with the introduction of a new watch mechanism.
This new Manufacture mechanical hand-wound calibre (BM12- 1975M), designed in close collaboration with the Group’s Manufacture Horlogère ValFleurier, is tailored to suit Baume & Mercier’s precise product requirements. It includes a set of unique technical characteristics and Baume & Mercier design features:
– Exclusive TwinSpir technology combined with a newly designed inertia-type balance wheel
– High-end decor finishes of the caliber : bridges with “Côtes de Genève” decor, circular-grained finished plate, blued steel screws, specific Baume & Mercier engravings
– Thickness: 3.5 mm / Dimension : 12 1⁄2 ’’’
– Adjusted to five positions
– Jewels: 18
– Power reserve: 90 hours
– Frequency: 4Hz (28,800 vph)
The Baume & Mercier Calibre BM12-1975M integrates advanced technologies developed by Richemont’s Research & Innovation teams. The TwinSpir technology is applied in a novel hairspring comprising a composite structure combining 2 layers of silicon, alternatively oriented and bound through a layer of silicon dioxide. This further layer acts also as a thermo-compensating element.
The TwinSpir hairspring, combined with an inertia-type balance wheel : enhances the precision of the movement in various positions and over time, limits the sensitivity to surrounding magnetism and ensures a greater resistance to small shocks and repeated vibrations.
A non-magnetic, light and corrosion-resistant material, monocrystalline silicon exhibits different elastic and thermo-elastic properties along various crystalline orientations of the material, as shown on Figure 2. This variation of response is known as the material’s elastic anisotropy. As a watch’s hairspring – the beating element responsible for the timekeeping accuracy and precision of the watch – expands and contracts during its oscillations, the elastic anisotropy tends to affect the oscillations’ evenness and consequently the timepiece’s chronometric performance.
This limitation is successfully overcome by the TwinSpir technology through the combination of 2 layers of silicon with different crystalline orientations (Figure 1) so that the variations of the Silicon Elastic Modulus is balanced, thus reducing the consequences of this natural property of the material. The silicon dioxide layer additionally binds the two silicon cores of the TwinSpir hairspring (Figure 3), and acts as a thermo-compensating element of the hairspring. Together with an outer layer of silicon dioxide, this enables stable performance across a range of temperatures (Figure 4).
The newly designed balance wheel of the Baume & Mercier calibre is an inertia adjustment type, as opposed to traditional index-pins assemblies. Index-pins assemblies have the rate adjusted through correcting the active length of the hairspring. By opposition, inertia- adjustment types offer the key advantage of a more vibrations- resistant rate setting, as the inertia-adjusting weights which ensure the precise adjustment of the watch rate, are securely held on the balance wheel between its arms and dedicated supports. 
