Actually, I'm sorry to be stubborn, but I found other pictures of what appear to be this exact car in a few other sources, all attributed to Buhne.
Identical details:
Slanted bonnet louvers
Contrasting light colored trim on wing edges
Windshield wiper position
Driving lights on cowl
Concentric circles (whitewall tires?) on wheels and bright center hubcaps
Triple-bar front bumper with number plate above
Trim on door under window
Shape and angle of door handle
Ribbed vent or step edge directly under door
Light-colored running board
Shape of curved lower edge of cloth hood
Diagonal "tension rod" over this curved lower section.
Woman in the car looks similar to and is wearing a similar hat as the one in the puzzle car.
I found other pictures of this car and similar Buhne ones with tiny light colored squares or ovals right behind the bonnet edge. Perhaps a coachbuilder's mark? I suspect we can't see the hood latch and door hinges on the puzzle car because of blacking out the red text, but a tiny light colored square is right where it should be behind the bonnet edge. Is it possible that your source might be wrong?
