Vacheron et Constantin
The mechanism in the Vacheron et Constantin Patrimony Extra-Plates watch has been produced since 1955, introduced as their bicentennial piece. The mechanism is only 1.64 mm. thick, making it, decades later, still the thinnest calibre to be found in a wristwatch. "Vachement Plates," as it were. I would say this watch is too fragile for normal use: for Black-Tie occasions only. This is Haute Horlogerie. Vachement belle . . .
The last photo shows a skeleton watch with the same Vacheron 1003 mechanism. I found this photo on the internet and modified it to present it here.