A Canadian friend of mine had a similar problem. He had been working in
the US for several years, and was returning to his new job in Canada, his
car filled with dozens of boxes of punched cards. The Canadian Customs
officers told him he would need to pay a duty (as I recall, it was fairly
stiff for the day--$5 a box or so) and my friend argued in vain for quite
a few minutes. Finally, he opened one of the boxes and said "look, these
all have data on them. They aren't useful for anything..." and the
customs officer said "Oh. These are USED cards. That's OK. No duty!"
"Ahh. You don't understand. We only use the holes."
-- Charles