[FirstOwner69]

Not sure this will help...
I just returned from a "visit" to the NCRS website since I haven't participated in the NCRS judging side of things for about 30 years. After searching the forums, I could not find a definitive answer, and my 1958 judging manual mentions nothing but a few stencils (for example on the driveshaft). The opinion seems to be that the paint dabs used on C2 and C3 Vettes were only put on a few cars a day selected for closer inspection.

I found this quote quite enlightening and amusing:
"1st-Generation Camaro restorations are similar to many of the Chevelle restorations I see - sometimes I think there's a contest going for who can pile on the most "restoration graffiti", almost none of which was on the cars when they left the plant. eBay auction restoration photos are apparently the standard .

Corvettes ('63-'67) had very little in the way of labels, stickers, stamps, and paint splotches on them, and NO fasteners had "paint marks" on them unless the car was one of the two selected each day for the off-line Quality Audit, which included a torque check of critical fasteners."

That said, I don't remember anything on my '69 truck's evaporator case other than the Harrison tag. I DO also recall wondering why all the crayon marks were on the firewall and cleaned up the underhood area by removing them. I would probably have removed a red dab on the evaporator case also if it had been crayon rather than paint.

If present, I'd expect it would indicate a successful charge or leak down test.