[rmason]

I've used International Reply Coupons as a ham. When hams 'work' each other they exchange something called QSL cards that are the size of a post card confirming the conversation. Speak with enough US States or foreign countries you can submit your QSL cards to qualify for awards like Worked All States (WAS) or countries confirmed (DXCC).

When working overseas hams, particularly when they live in the third world it was common to mail them enough IRC's to cover the return postage for them. Now while QSL cards haven't disappeared most of it has moved to the web and digital confirmations.