This is a very limited timepiece made for a Montgolfiere enthusiast or balloonist.
The solution to indicate time in the upper part of the watch while showing the day and date in the lower area. There seems to be a sapphire glass to separate the movement from your eyes, so you have a free view on the gears.
This timepiece is housed in a whitegold case and sized at 40mm. Powerreserve with automatic winding is 40 hours. Each watch is limited to 5 pieces only.
There are more variations as well dedicated to other cities including Versailles, Bordeaux and Bagnols. The dials are different, not only in color, but also bear a different balloon. Colors include green, blue, bordeaux red and brown. For more information, please visit the Vacheron Constantin homepage.
Pictures courtesy of Vacheron Constantin.