Vienna regulators with sweep second hands are quite rare and very desirable. These photo's detail how the mechanism is set up.
Winding Drum - Note that the screw that holds the slotted washer in place is also the stop screw for the maintaining power gear - see previous photo to understand how it works
Winding Drum - Note that the screw that holds the slotted washer in place is also the stop screw for the maintaining power gear - see previous photo to understand how it works
in this box: