Red A/C box assembly mark

[IronCanine]

I have spent a bit of time trying to suss out a pattern and reason for the red mark that appears on some A/C boxes just above the Harrison decal. They're doesn't seem to be a pattern with regard to assembly plants. And they also appear episodically on GM cars of this era. Member F.A.A.benny reports seeing them frequently in Pontiacs. Does it indicate the system has been charged? Is it simply an assembly check? I figured it was time to throw it to the collective and see if anyone-maybe some of you that dabble in other worlds like vettes, Chevelles, and the like-may have some insight. I have seen them on St. Louis trucks, so I'm putting the mark on our build...but I've seen more trucks that don't have the mark. Anybody got the scoop?...or at least some ideas?

Thanks for any insight.

Brad

[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.

[IronCanine]

Thanks for the insight Jim. I must confess, I have a weakness for the graffiti. But the idea that it could be a "spot check" mark would be consistent with the fact that I've seen many more without than with. "This unit is charged" seems like the most obvious explanation as well.

[IronCanine]

Red Dot alert...Thanks to Jim(FirstOwner69) spotting this new to me location on a truck Jocko posted in the Craigslist thread. No SPID or VIN...so plant unknown at this point.

[IronCanine]

Here's another one I banked a while back. 72 Flint Blazer. Dot at the bottom.