The fusée system was popular in antique clocks and pocketwatches, but it’s rarely seen in a wristwatch. It can be very valuable, though: it helps ensure that the mainspring winds down evenly. As the watch winds down, the 18-cm-long chain unwinds from the fusée at 2 o’clock and wraps itself around the mainspring barrel, at 10. Thanks to the sapphire-crystal dial, all these machinations are visible, and you can see past the blued-steel hands on the time display at 12 o’clock to watch the chain as it moves. Additionally, the Grand Voyage II has a power-reserve indicator at 3 o’clock, so you can chart the course of its 50-hour span. Then, when you wind the watch again via the crown, you can see the chain transfer, spinning off of the barrel and winding back around the fusée.
3. The movement has a whopping 939 components.
The fusée chain alone has 585 parts, so the Grand Voyage II is already in the stratosphere when it comes to components. Separate from the fusée, the movement – known as El Primero 8805 – has 354 components, and 173 of those make up the Gravity Control module. The 8805 runs in 53 jewels; it’s a high-beat, turning at 36,000 vph. By itself the movement is 5.85 mm thick and 37 mm in diameter.