I imagine there is a clear and distinct line between "I've never seen one of those" and "I can remember exactly how those sound". The sound of sliding that handle over the card is ... distinctive. I can discuss it with someone, slide my hand left and right, and say "shunk, shunk" and lots of people will very clearly remember them.

“Never heard of these”, meanwhile I was remembering a credit card that I used so often that I wore the coloring off the raised numbers.

And I guess if one has never seen these, I need to explain. In order to leave an impression on the carbon paper (I should probably explain that, too, huh?), a fair amount of pressure was needed (those old card imprinters didn’t require a gym membership, but a child could not operate one). That rolling pressure would eventually wear on the surface of the card, and turn the numbers white when the outer layer wore through.

I suddenly feel very old.