Cards are from before my time. The blank cards I've seen had printing on one side, and usually some sort of title area. so you could get orientation correct.

Cards are from before my time. The blank cards I've seen had printing on one side, and usually some sort of title area. so you could get orientation correct. The punched cards I've seen were all hand numbered. The stripe, I think, was mostly a quick check. if it looks like a line, they're probably in order. if there's a spot that looks weird, you can check that range quickly. I don't think the failure mode was like someone grabbing your deck and throwing it in the air, it was more they got dropped, stayed mostly stacked, but you could quickly file the strays in the right order. and be pretty confident the cards that stayed stacked were right. if you've got a blurry spot of the line, you can quickly check that section. so, yes? I think the stripes worked? Again, before my time, this is lore handed down from professors. I think if you secretly swapped 2 cards, and they didn't notice, they would hunt you down and beat you up. IIRC, the cards did wear down, but there were duplicators, that would read old cards and punch fresh ones. Obviously, if something was torn or damaged, you'd have to fix that by hand. I think I've seen one once, but I don't recall exactly where. edit- https://en.wikipedia.org/wiki/IBM_519#514 https://en.wikipedia.org/wiki/IBM_519#514 <- that's not what I remember, but they did exist.