How do I know when a sample is good enough that I'd actually put my name on it?
Use the golden sample test: would you be comfortable if every future unit looked exactly like this one, flaws included? Sign, date and seal the approved sample, keep one yourself, give one to the factory, and give one to whoever does your QC, that physical object, not your memory of a WhatsApp photo, is now the legal and practical definition of 'correct'.
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The clearest explanation of why a physical, signed sample, not a spec sheet, is the real definition of 'correct' once production starts.