especially those laser printed notes........

The Xerox one needs special invisible ink or yellow microdots, right at the end.
Canon, Toshiba and Ricoh print yellow microdots, either 0.1 mm or 1mm.

Names given are real.

Slashdotters having fun with it here

Favourite comment so far:

I was right! (Score:5, Funny)
by Kenja (541830) on Monday November 22, @06:31PM (#10893064)
(http://www.netweasel.com/)
This is why I always print my ransom letters using an old daisy wheel printer.
[ Reply to This ]

That's not a daisy wheel printer (Score:4, Funny)
by commodoresloat (172735) on Monday November 22, @06:38PM (#10893170)
(http://informationtornado.com/)
It's Microsoft Word. There was no printer available in 1972 that could have printed those....
Oh, sorry. Wrong discussion.