I will assume that the car passes the visual overspray check.
Washer Nozzels, wiper linkage, all trim, glass, front doghouse bolts.
Any Fastener which hold the fenders or hood or any latch on the front.
The edge on round bead fuzzies on the door and 1/4 windows.
Door handle or lock gaskets check these close... if the gaskets have been replaced then you need to look and question deeply.
If it passes these major checks then you need to look to make sure the paint job is not "too good"
Check the seams where the quarter meets the roof they are leaded and are usually wavy and most have checks and minor pinholes here, if you follow this seam to the rear glass most cars will have some grind marks in the lead where the edge and the rear glass trim meet.
On the A pillar at the Top most have some heavy swirl sanding/grind marks
Run your finger around the jambs and feel for any ridge or any faint roughness or overspray, use a flash light and open the doors up and hood up if you see original fasteners and shims with no overspray on them and the correct patina on the fasteners then you should probably get a few opinions if you want to preserve it or maintain the absolute originality.
The paint was usually the first casualty when the early nice restos were being done as those cars were easy restos.
My father who collects Early Flathead Fords used to say that they restored far too many cars in the early days that should have never been restored most would now be considered prized pieces in collections.
There is a certain look to original lacquer, most guys who like unrestored cars can spot the patina while walking by.
I walk down isles and isles of cars of restored cars, when I see an original unrestored 6 cylinder car it will hold my attention and be the subject of more photos than any restored COPO or Z28 at the show, now an unrestored COPO or Z28... nice