I saw this and couldn't help myself from taking it. I remember thinking it would have been far easier for the postie to lift the letterbox lid and just slide the whole lot in, rather than stuffing a tightly folded A4 envelope through that narrow slot.
Forgot about punch cards, the pay office of one place I worked at were paranoid about the payroll punch cards. If we had a glitch in anything else, not a problem, but if the payroll went belly up it was a really big issue.