Ulysse Nardin Vintage Complete Calendar Chronograph.
Better than that, a Chronograph with a complete or perpetual calendar AND a moon phase, but we cannot deny that this watch oozes class.
Even better, yellow gold adds class and elegance.
The lugs are very nice, too. The case is 37 / 38 mm, which is a perfect size.
I have hard time dating this watch, but I would say from the Fifties?
Screw-in case back:
As for the movement, I don't really know.
Always a pleasure to see such watches and to share them.