Quality Control Before 1940-S?

In another post, I was asking if somebody knows of any sort of quality control in place for US stamps before 1940s.
Do you know of any references to such a process, please?

I am still waiting for quality control for stamps in the 2010s.....

There must be something on the line of 'checklist' before delivery

I don't for a second think it is 100% applicable, but when I was in the Navy, I filled in for our Postal Clerk when he injured his leg hauling a mailbag down the ladder from the flight deck to the post office area of our Destroyer (ie, he severely sprained his ankle playing flag football). I had to receive stamps (both 'normal' and official) as deliveries, and we always did inventories of stamps, envelopes and funds weekly. All that was ever checked on our 'receiving' end of things was number - did we receive 400 stamps? check. Did we receive 4 sheets of the $0.25 official stamps? check. does the cash till check? check.. ok, see ya next week. Nothing to do with production quality checks, but at an official naval postal station (while there, I stamped the incoming 'Naval Cover' mail with the ships handstamp.. being a collecter, I tried my best to give nice, clear cancels), all we were concerned with was number received matching what was ordered, or expected. They couldn't care less how badly they were printed. This was mid-late 1987, for a frame of reference.

Of course there had to be. As an example, #634, the extremely common 2c Washington type I of 1926 that was printed in the multi-millions has only one major error (imperf vertically) that is quite rare.

Do you expect perfection? As jaxom100 notes, the printers are relatively sloppier today. In the period you note, there was no requirement for perfect centering with perfect perfs, if that is what you mean. The equipment quality of the time would not allow that nor was overall production geared to pleasing collectors.

I have read that there were 8 inverted center sheets of the 5 cent Beacon; all were caught and destroyed. There were several other sheets of C3a caught and destroyed as well. And most pre-1940 errors are scarce to rare so someone must have been doing a decent job checking.

If you are a printing contractor there are technical specs and QA/QC requirements that are a part of your contract and you like to get paid in a timely fashion. If you are the government self performing there are still tech specs and best practices but nobody is going to hold up your progress payment if things are not the best they could be.