Jaeger-LeCoultre’s 39mm Master Ultra Thin case (henceforth known at MUT) is one of my absolute favorites. It is the perfect size for me, the perfect size for a dress watch, and no matter the complication, it just works. Take, for example, two introductions in this line from the past two years – 2011’s Master Ultra Thin Moon and 2012’s Master Ultra Thin Tourbillon. Both of these replica watches are simply divine (and the latter is one of the few tourbillons I would actually wear in public without feeling like a true, well, you know what I mean). So, for 2013, Jaeger-LeCoultre has gone ahead and introduced a superb new replica watch in this same ultra-thin 39mm case, and it just so happens to be my favorite complication – a perpetual calendar.
So what is this replica watch exactly? Well, it’s not exactly brand new, in the sense that it uses JLC’s ultra-thin modular perpetual calendar, in this case called the caliber 868. This is a self-winding perpetual with 336 parts and 46 jewels, that remains just 4.72mm thick. Impressive, certainly. So impressive in fact that this perpetual calendar fully cased is just 9.2mm thick, while the less complicated watches I mentioned above come in thicker! The MUT Moon is 9.9mm thick and the tourbillon is 11.3mm thick. And, for those who believe in traditional watchmaking, the ultra-thin perpetual calendar is one of the holiest of calibers. So this watch, in a traditional 39mm case, strikes a lot of chords with purists.
And purity is what this watch is about. The replica watch uses three registers plus a moonphase at 12 o’clock to display everything from the day of the week to the date to the month, plus two additional pieces of information that are not necessarily found on all QPs. The first is an actual year window placed at 7 o’clock. This is typical of JLC perpetuals, and while I don’t think it upsets the balance of this dial too much, I personally feel the watch could have been made without it. It’s not a bad thing, but dial symmetry is something I look for in dress watches. The practical reason that this display is here is that this caliber doesn’t display leap year indication on one of the registers, so it’s needed to know if there are 366 days in this year, or just 365.
The other aperture on the JLC MUT Perpetual not typically found on QPs sits just above the axis point towards 12 o’clock. As evening falls, this aperture slowly turns red, indicating the wearer should not adjust his or her watch. For those who don’t know, changing a perpetual calendar during the hours of 10pm and 2am (each manufacture has its own range, but this is a rough estimate) can dramatically damage its gears. The reason is that during these hours, the gears are actively engaged in changing the date. This JLC MUT Perpetual Calendar gives you a fool-proof way to know when NOT to change your watch. Clever. During the rest of the day, the small aperture returns to the same color as the dial.
And speaking of dials, you may have noticed from the pictures above there are a few different options, and this is where things get really interesting. As with most truly “complicated” watches, Jaeger-LeCoultre will offer this MUT Perpetual precious metals – rose and white gold.