A friend of mine worked for the US Census Bureau for a while. Among their myriad binders and forms, etc. was a page full of tear-off perforated wallet size cards which contained no text or information on them whatsoever other than “do not distribute this card” printed on the back. And no, I have absolutely no idea what the purpose of these things was supposed to be. Nor apparently does anyone else.

So of course he dutifully tore them all off and quite deliberately handed them out to people. He gave me one. I might still have it someplace.