JLC Duometre Chronograph Moon - What a Combo!

Launched at the Watches & Wonders 2024, the Jaeger-LeCoultre Duometre Chronograph Moon is watchmaking at its best.

But first, my two Duometre...

First, the Duometre a Chronographe (above)

And the Duometre a Quantieme Lunaire... And then there is the new Chronograph Moon (below)

The Platinum version...

And the Rose Gold version.

Fitted with the new Calibre 391, the Chronograph Moon is a combination of two previous iterations - the Duometre a Quantieme Lunaire and the Duometre a Chronographe, both of which I am featuring here.

I have always liked the Duometre range and as luck would have it, was able to acquire the Duometre a Quantieme Lunaire Limited Edition from the secondary market. This version comes with a white grand feu enamel dial.

Prominent in the Duometre range is the 1/6th second - also known as Foudroyante. Both worked differently in the Quantieme Lunaire and the Chronograph.

What's really interesting about the Duometre range is the movement.

Featuring two barrels, each barrel powers diffrent function - one the complication and the other powers the gear train for timekeeping.

Next up is the Duometre Chronograph...

Again, this is another Limited Edition piece in white gold case and a black dial.

Unlike the Quantieme Lunaire, where the time sub-dial is on the right the time subdial in this case is on the left at the 9 o'clock. The right sub-dial is the chronograph sub-dial with a digital reader to boot.

And unlike the Quantieme Lunaire, the Foudroyante function does not activate until the chronograph is activated. With the Quantieme Lunaire, the Foudroyante function is always constantly beating.

The movement also has 2 regulating organs - one for the chronograph and one for timekeeping. In this way, the accuracy of the timepiece improves as one barrel powers the chronograph and the other the time telling mechanism.

The chronograph is a column wheel (see below)...

As one would expect, the finishing on the Duometre is very well done.

Now back to the newly launched Chronograph Moon - this is a combination of the Quantieme Lunaire and the Chronograph...

Operating under the hood is the new Calibre 391 which I understand was modified from the 381. Whatever the case, it's no slouch and I suspect the movement under scrutiny will stand well on its own.

Between the platinum and the rose gold version, which one looks more appealing to you? For me, I still like the white metal but if only they could have done it in enamel, that would have been an outright winner for me.

JLC Duomètre a Quantième Lunaire - A Technical Feat

The Jaeger-LeCoultre Duomètre à Quantième Lunaire is one of those timepieces that is not only techically impressive but has the beauty to match too.

Since the launching of the Duomètre range, I've always admired the technical feat as well as the concept of separating isochronism from other functions like time and date display and even chronograph measurement. I'll come to that later...

In 2014, the manufacture in Le Sentier went one further and introduced the Duomètre à Quantième Lunaire with a Grand Feu Enamel dial. Limited to 200 pieces, the dial side is as beautiful as the movement.

The dial layout is simple yet breathtaking.

At the 9 o'clock (above) is the moonphase and date display. I would have thought that the blue hands were heat oxidized but they are painted. Still, they give a nice contrast to the milky white dial.

Adjacent at the 3 o'clock position (pictured above) is the time display. At certain angles, the hour and minute hands has a golden hue but at certain angles, grey. And right at the 6 o'clock (pictured below) is the display for the 1/6th second display - also known as Foudroyante.

The jumping seconds ensures the chronometry and one of the feature of this Duomètre is when you pull the crown. When you pull the crown at the first position, the Foudroyante hands returns to the zero mark and the seconds hand stops just like with the hacking seconds of a normal watch. But wait! When you pull the crown again to the second position, the seconds hand resets to zero too. Much is said about time setting accuracy and the Grand Maison has done a wonderful job of including the double zero resets in the Duomètre.

Now for the technical wonder in Calibre 381. The Calibre 381 is beautifully laid out and is made from German silver. German silver, also known as maillechort, is not actually silver and its composition of Zinc, Nickel and Copper gives it the slight golden hue. Movements made from German silver are said to be anti-magnetic and anti-corrosion making it a good material for movements. But it is also said that German silver is really hard to work with.

Duomètre comes with the "Dual Wing" power system. What this means is that the double barrel Duomètre has one barrel supplying power to the balance (right barrel in the picture above - regulateur) and one barrel supply power for the other functions like time and date display and in this case, the moonphase. Each barrel provides an impressive 50 hours power reserve.

Not only is Calibre 381 a magnificent movement, the finishing is also top notch. It stands up to close scrutiny. The anglage is beautifully done and the blued screws gives the movement a nice contrast.

The sunray decoration on the movement bridges are radiating from (or towards) the balance.

One of the key feature of the Dual Wing concept is the separation of the isochronism from the other functions. When we pull the crown to set the time, the escapement continues to oscillate which ensures that the amplitude is not lost during time setting. The balance beats at 21,600 vph.

And what about winding the timepiece? There are two power reserve indicators beside the Foudroyante sub-dial. The + indicates the power is at its max and when the power reserve runs down to zero, it will be at the - mark. One gives the power indication of the regulating organ (between 7 and 8 o'clock) while the other shows the power left on the other barrel for time/date and moonphase indication. Winding the clockwise direction powers up the escapement barrel while turning the crown anti-clockwise winds the functions barrel.

The Duomètre has always represented one of the best the Grand Maison has to offer. And now, they have released the new Doumètre Spherotourbillon... to die for really. But I am happy with what I have - the Duomètre a Quantième Lunaire with a Grand Feu Enamel dial.