Leroy Osmior Chronometre Observatoire

Luxury watch manufacture Leroy is renewing ties with traditional Haute Horlogerie through its new timepiece Chronomètre Observatoire from Osmior collection. This authentic timepiece is a reference to the inventions of the 18th century master-watchmakers and features the fundamental principles of horological science, inspired by the work of Pierre Le Roy (1717 – 1785), “the father of modern chronometry”.

The Osmior Chronometre Observatoire is equipped with the new-generation hand-wound L200 manufacture movement entirely developed and built in Le Sentier(Switzerland) and equipped with an escapement with direct impulse on the balance, balance-spring with double terminal curve and parallel-mounted twin barrels. The movement is housed within an elegant round gold case (5N red gold, white gold or two-tone 950 palladium and 5N red gold) with a 38 or 40 mm diameter, framing a refined solid silver dial adorned with hand-guilloché “barleycorn” motifs inspired by 19th century Leroy pocket watches.

The applied Arabic numerals are made of gold and delicately cabochonné, meaning each is hand-polished and domed. The steel hands based on an exclusive Leroy design are open-worked and the 98-hour power reserve is visible through a lozenge-shaped aperture at 9 o’clock that is deliberately subtle in order not to disturb the perfect aesthetic balance between the various dial elements.

The development of the new three-hand L200 chronometer movement pays tribute to Haute Horlogerie in a manner entirely in tune with the history of Leroy, while also backed by new technologies aimed at achieving optimal precision.

This original calibre, featuring an escapement with direct impulse on the balance (1 impulse/1 oscillation) that transmits constant energy to the regulating organ and ensures its excellent rating precision, stems from the imagination and research of master-watchmaker Karsten Frässdorf.

The balance with its 4 adjustment screws is equipped with a balance-spring produced by a company belonging to the Festina Group (MSE) and comprising an unusual double terminal curve. The combination of inward and outwards curves is conducive to isochronism by enabling perfectly concentric deployment in a vertical position and eliminating any potential imbalances described in watchmaking literature as the “Grossmann effect”.

It also serves to neutralise the “Caspari effect” based on the discoveries made by Pierre Le Roy whose empirical approach showed that there is for every balance spring a certain length that endows it with perfect isochronism. By using the “Brun Cage” (an invention by the watchmaker M.J. Brun in around 1900), the position of the balance-spring stud may be varied by 360 degrees, thus enabling the setter or timer to choose the best pinning point and also to determine the outer terminal curve. The calibre oscillates at a rate of 18,000 vph (2.5 Hz) and features parallel-mounted twin barrels and 42 jewels including four synthetic diamond jewels.

The Chronomètre Observatoire model provides a central display of the hours and minutes via cut out “Corteault” shaped steel hands and also features the stop-seconds function. A small subdial at 6 o’clock shows the passing of the seconds by means of a “duplex” jump (thus named in tribute to Pierre Le Roy and his Duplex escapement) consisting in a short jump followed by a longer one. A lozenge-shaped aperture at 9 o’clock reveals the disc providing the 98-hour power-reserve indication (IRM). From 0 to 60 hours, the disc remains the same colour as the dial, while from 60 to 80 hours, it switches to white; and beyond 80 hours appears in red to signal that the autonomy is nearly depleted: a highly appreciable, useful and extremely discreet function entirely in tune with the dial.

The design also scrupulously respects the signature characteristics of the works of art created by Leroy in previous centuries, while also corresponding to current tastes and trends. The round case embodies subtle stylistic sophistication expressed in three versions: 5N red gold, palladium-coated (non rhodiumed) white gold and a two-tone variation. It is composed of three parts: a satin-brushed bezel, a circular saint-brushed case middle and polished gadroons. The glare-proofed sapphire crystal case-back enables the collector to admire the beauty of the calibre with its entirely hand-crafted finishes.

The solid 925 silver dial highlights the central “barleycorn” guilloché decoration performed in keeping with the finest Haute Horlogerie traditions. The applied gold Arabic numerals stand out clearly against the snailing on the outer segment, while the finely snailed small seconds subdial ensures perfect visual balance.

The dials come in a choice of five colours: opaline silver-toned, Leroy blue, Leroy champagne, rosé champagne and slate grey. The hour-markers match the colour of the gold case, while the blue, rhodiumed or “black gold” hands may be selected according to the customer’s personal preferences. The movement wheels are produced and adorned in keeping with the highest quality standards. Also demonstrating complete respect for the ground rules that make an object truly high-end, the pinion leaves are polished using a wooden grinding wheel and the ratchet-wheels finished using the ”Mât de Genève” (Geneva Mast) process, an ancient decorative technique that give them an anthracite colour, while the other steel parts as well as the winding mechanism are specular polished (also known as black or mirror polishing). The bridges are bevelled and frosted to create a bronze-tone colour. All the screws are blued from the outset to avoid oxidation, while the screw heads are specular-polished and even the profiles of the collets are also polished.

The timepiece is tamed with a hand-sewn alcantara-lined alligator leather strap secured by a pin buckle or folding clasp.

Each Chronomètre Observatoire watch is individually numbered and delivered with its own chronometer rating certificate issued by Besançon Observatory. The latter tests the entire watch ‘head’ (meaning a fully cased up model not yet fitted with its strap/bracelet) in a comprehensive manner involving 15 consecutive days of testing in every position, and each mainplate is hallmarked with the famous “Viper’s Head”.

Technical details
Mechanical hand-wound movement
Dimensions: 15’’’ in diameter & 4.5 mm thick
Shape: Round
Jewels: 38 in sapphire and 4 in diamond
Power reserve: 98 hours
Frequency: 18,000 vph (2.5 Hz)
Barrel and wheels: in CuBe (copper/beryllium)

Escapement and regulating organ
Direct impulse on the balance (1 impulse/oscillation)
Unlocking lever with 2 diamond pallets
Unlocking adjustable diamond impulse pin
Brun cage, balance-spring stud and pinning positions variable over 360°
Balance-spring with double terminal curve: 1 inner curve and 1 outer curve

Central hours and minutes
Small second at 6 o’clock
Power-reserve indicator at 9 o’clock

18K 5N red gold – non-rhodiumed 18K 150PD white gold – two-tone non-rhodiumed 18K 150PD white gold and 5N red gold
Diameter: 38mm or40mm
Thickness: 9.7mm (38mm), respectively10.50mm (40mm)
Three-part, round
Circular satin-brushed case middle – satin-brushed bezel and polished gadroons
Polished caseback and dial fitted with glareproofed sapphire crystals
Water resistance to 3 ATM

Solid 925 silver
Applied 18K gold Arabic numerals
LEROY steel hands: rhodiumed, 5N gold-plated or anthracite , or blued
Lozenge-shaped power-reserve indnciator at 9 o’clock
Barleycorn guilloche central motif
Snailed hours segment
Finely snailed small seconds subdial
Transferred minute track
Colour variations: opaline silver-toned – Leroy blue – Leroy champagne-toned – rosé champagne – slate grey

In hand-sewn brown, black or blue alligator leather with large square scales and alcantara lining
Pin buckle or double-blade folding clasp in 18K white gold or 5N red gold

Each Chronomètre Observatoire timepiece undergoes the chronometry certification procedure conducted at Besançon Observatory and earns a chronometer rating certificate that is delivered with the watch.

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