Sometimes those "check" marks don't mean much.
As a hobby, I restore vintage ham radio gear and Hallicrafters of Chicago was one of the biggest U.S. manufacturers. Their "crowning achievement" was the SX-88 shortwave receiver introduced in 1954 and sold for a couple of years. Its 1954 price was $595, equivalent to about $7,000 today so it wasn't cheap but the design and build was excellent and every soldered connection had a little red dot of inspection paint to show that it had been inspected after production.
I bought and restored one about 12 years ago and it worked fine except for intermittent noise on one frequency range. I traced the problem to a connection with a nice dot of red inspection paint but no solder had ever been applied. The mechanical connection had been fine for decades but finally wasn't, so much for the inspection paint. I suspect some high school kid was given a job on the line putting a little dot of paint on every soldered connection to make it look inspected.
When I was in elementary school I read a biography of Walter Chrysler who was the founder of Chrysler corp. When he was a young apprentice, he was working as a railroad mechanic and he said one of the most valuable lessons he learned as an apprentice was to always make your own marks when setting up the drive cylinders on a steam locomotive instead of trusting that the person before you did it correctly. I have been reminded of his sage advice many times over the years.
Rodger