May 23, 2024

The Only Watch organisation published the entire list of unique pieces that have been donated for the charity auction. Since we’ve been covering some of the highlights, we won’t ‘bore’ you by covering all of the 43 watches (there’s more news and interesting stories in the world of watches). However, we just have to share this is one, because we think it is one of the absolute highlights. It might not have the highest retail price, nor will it fetch the highest hammer price. For us watch nerds, an observatory chronometer that features a bunch of technical feats to improve the chronometric rates, is a sheer pleasure. And when you realize it’s made entirely in aluminium (and by that, we mean the case, dial, bridges and main plate), that makes it even more special. Here is the superlative Leroy Chronomètre Observatoire for Only Watch that is entire crafted in aluminium. 

LEROY_Pendulette-de-voyage_Al_no65The choice to make the unique piece for Only Watch in aluminium, was inspired by an aluminium travel clock from the brand’s museum. This aluminium travel clock that dates back to 1894, features a grande sonnerie, central seconds hand and alarm function, and is signed “L. Leroy & Cie –Montpensier. Palais Royal. Paris.”

While the travel clock only features an aluminium encasing, the use of this material for the one-off edition of the Chronomètre Observatoire, from the Osmior line, was taken a few steps further. The case, dial, main plate and bridges are all made in aluminium, and if you wonder if that makes it unique in the history of watchmaking, we have to say that it doesn’t. The use of aluminium for main plate and bridges is extremely rare, and the only other aluminium wrist watch that that takes the use of aluminium this far, that we can think of, is the Octa Sport by Francois-Paul Journe.

As already mentioned in the intro, this is an Observatory Chronometer, meaning it has been build for precision timekeeping, and tested and certified by an obsevatory; in this case the Besançon Observatory. Leroy has an impressive track record when it comes to chronometric competitions, and they’ve won no less than 384 gold medals. The most recent gold medal received was in 2013, at the International Chronometry Contest in Le Locle.

Each Chronomètre Observatoire, and also this pièce unique for Only Watch, is tested by the Besançon Observatory, and comes with an individually numbered chronometer rating certificate. The entire watch ‘head’ (meaning a fully cased up movement without its strap) will be tested comprehensively – this involves 15 consecutive days of testing in every position. The watch’ mainplate is hallmarked with the Viper’s Head, which is only allowed for watches tested and approved by the Besançon Observatory.

Leroy Chronomètre Observatoire only watch 2015

Soon we’ll present the Leroy Chronométre Observatoire (and their new tourbillon) to you – extensively as it should be done – and we’ll explain all the nitty gritty details of this magnificent timekeeper. For now we’ll focus on the use of aluminium, the little red rhombus that is next to the 9. And of course we’ll show you some more images of the stunning calibre L200.

The aluminium dial has a two-tone silver colouring, and is surrounded by a rail track minute index. The hour indexes are applied Arabic numerals, except at 6 o’clock the second sub dials occupies this place. Just below the 12 is the brand’s logo applied, and at 12, 3 and 6 are small applied indexes (in between the rail track) that are filled with luminescent material. The steel hands are rhodiumed and also filled with luminescent material.

Leroy Chronomètre Observatoire only watch 2015

Next to the 9 is not such an applied index, but a rhombus-shape aperture that reveals the power reserve indicator. From 0 to 60 hours, the disc of the power reserve indicator 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.

The 40 mm-diameter round case is crafted from an aluminium alloy that has been treated to make it even harder and more resistant. The anthracite grey colour is created by means of anodisation. The circular satin-brushed bezel features polished gadroons, and the polished rear bezel is engraved with the inscription “Pièce unique” and “ONLY WATCH 2015”. The sapphire crystal on both sides is glare-proofed. The watch comes on a hand-sewn alcantara lined alligator leather strap and is close by a pin buckle, which is also made of aluminium.

Leroy Chronomètre Observatoire calibre L200

Through the crystal in the case-back you can see (or better: admire) the stunning calibre L200, of which the main-plate and bridges are also made of aluminium. Naturally everything is entirely hand-finished! For instance: the pinion leaves are polished using a wooden grinding wheel. The ratchet-wheels are finished using the ”Mât de Genève” (Geneva Mast) process, which is an ancient decorative technique that give them an anthracite colour. Other steel parts as well as the winding mechanism are black polished (also known as mirror polished). The bridges are bevelled and frosted to create a bronze-tone colour. All the screws are blued to avoid oxidation, while the screw heads are specular-polished and even the profiles of the collets are also polished. All together the Leroy Chronomètre Observatoire is lavishly finished and a real feast for every watch aficionado.

Leroy Chronomètre Observatoire calibre L200

Some specifications – Leroy Chronomètre Observatoire unique piece for Only Watch 2015

  • Case: Anthracite grey anodised aluminium (316Al), 40 mm in diameter, 10.50 mm thick, water proof to 3 ATM (30 meters)
  • Movement: Calibre L200Al 1/1, 38 jewels and 4 jewels in diamond, power reserve 98 hours, frequency 18,000 vph (2.5 Hz), 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 over 360°, variable balance-spring with double terminal curve: 1 inner curve and 1 outer curve (these details will be explained in our upcoming hands-on review of the Chronomètre Observatoire)
  • Strap: hand-sewn alcantara-lined alligator leather strap and is close by a pin buckle, which is also made of aluminium

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