The Reverso à Triptyque is certainly one of the maddest creations from Jaeger Lecoultre. 

To make it short, I would say that this is the only watch which depicts the time in three different ways, on three sides.

Indeed, on the recto, you have the civilian time, on the verso the sidereal time, and on the carriage, the perpetual calendar.  About the perpetual calendar, here is an extract of the owner's manual, explaining how it works: 

" In the reversible case carriage, Jaeger-LeCoultre has pulled off the feat of adding the measurement of a third dimension of time: the instantaneous perpetual calendar. What makes this a major feat is that the calendar is actuated mechanically by the main movement housed in the reversible case. With a retrograde date display, the instantaneous perpetual calendar is activated by an ingenious transmission system from the movement to the mechanism housed in the carriage. Every night at midnight precisely, the calendar advances instantaneously by one day."

The three sides of the Reverso à Triptyque: 

To be more precise, it is announced as one of the most complicated fine time piece, it houses, according to Jaeger-Lecoultre, the following 19 complications: 

- Day/Night Indicator on 24-hour display

- 60 second tourbillon with seconds indicator 

- Ellipse isometer escapement 

- Sidereal time 

- Zodiac calendar 

- Sky chart 

- Sunrise time 

- Sunset time 

- Equation of time 

- Case transmission system in carriage 

- Perpetual calendar 

- Instantaneous perpetual calendar 

- Day of the week 

- Date retrograde system 

- Date 

- Month 

- Leap year 

- Moon phase and age 

- Date-change power-reserve

The way they count the complications always left me perplexed. For example, when you logically count the perpetual calendar as a complication, you cannot add the day, date and month, as they are part of the perpetual calendar... 

BUT Jaeger Lecoultre used the same method as other brands here. 

For that watch, the Manufacture registered 5 patents, for the case locking system, the three faces, the ellipse isomer escapement, the zodiac calendar and the periodic impulse stop system for the calendar control. 

No wonder why the Reverso à Triptyque required 4 years of research and development! 

A few words on a specificity of this Reverso, its tourbillon, which has an " ellipse " escapement, which was clearly inspired from the marine chronometers and their detent escapement. I wonder if it is unique in a wrist watch, as I cannot remember if Girard Perregaux didn't use it in some of their Tourbillon with Bridges, but one thing is sure, it is pretty uncommon! 

While we are at it, here are some pictures of the Cal 175, made of 642 parts:

This is a superlative watch from an horological point of view, and also physically. 

The platinum case is gigantic in its proportions ( 55 x 37, 7 mm big, 17, 9 mm high ) and very heavy, even if I couldn't weigh it precisely, but handling it is an unforgettable experience, as well as putting it on my wrist. This is THE major issue of this watch, for sure... You really need to have a very big wrist to be able to wear it. 

Truth to be told, I am very impressed by the concept, the madness and the talent required to make such a watch. 

Still, I am not very fond of the recto dial, because I dislike tourbillons making a hole in the dial, from a personal point of view, even though this Tourbillon is original and very nice looking. 

I much prefer the two other sides, the verso, with its sky map, which is truly sublime, and the perpetual calendar inside the carriage. 

The platinum was the first version, limited to 75 pieces, followed by three ( maybe a bit more ) white gold versions: One Dark Grey " Clous de Paris " limited to 20 pieces, one Light Grey limited to 30 pieces, and an amazing Black for Hong Kong, limited to 3 pieces. 

The Limited Edition to 20 pieces: 

The Hong Kong Edition, 3 pieces: 

Seeing the platinum version after all these years is something magic, an experience I wanted to share with all of you. 

Best,

Nicolas