The Watch: The Duomètre line represents Jaeger-LeCoultre at its most technically ambitious. The concept is called Dual-Wing: two independent power sources within a single movement, united by one escapement. One mainspring powers the timekeeping (escapement and balance), and the other powers the display of time and complications (hours, minutes, date, moon phase). The crown winds them separately: clockwise for the timing barrel, counterclockwise for the functions barrel. The point of this architecture is to isolate the regulation from the energy demands of the complications, so the chronometric rate stays consistent regardless of what the rest of the movement is doing.
Reference Q6042420 is the Quantième Lunaire in 42mm 18k rose gold. The caliber 381 is hand-wound, 374 components, 40 jewels, beating at 21,600 vph with a 50-hour power reserve. The movement is built on plates and bridges in untreated German silver (maillechort), which gives it that warm yellowish tone visible through the caseback. The finishing is among the best JLC has ever produced: Côtes de Genève rayonnantes radiating from the balance wheel center, chamfered and polished bridge edges, heat-blued screws, and perlage on the main plate.
The dial carries date by hand, moon phase for both hemispheres, jumping seconds showing 1/6th of a second increments, and twin power reserve indicators. It's a complicated watch, but the layout is architectural rather than cluttered.
This 2012 example is in very good condition and comes as a very full set.
Condition: Very good. Some marks on the case.
Includes: Box, papers, 18k rose gold deployant clasp, 18k rose gold buckle, loupe, and pusher.
