INTERNATIONAL REPLY COUPONS
Most DXers are familiar with the International Reply Coupon or more commonly known as an IRC. The IRC was first introduced on October 1, 1907. Its purpose in Amateur Radio, but even more so for DXers, has been an international postage type of money system. The Universal Postal Union (UPU) designs, prints and distributes the IRCs to the UPU member nations. A DXer in one country could theoretically send one IRC from his country to a DXer in another country. The receiving station can then take the IRC to his post office and exchange it for postage for "the minimum postage for an ordinary priority letter-post item or an ordinary airmail letter sent abroad for the reply". In most countries one IRC is sufficient for the minimal size envelope back to the sender. There are some however that requires more, even though this totally conflicts with the UPU. W9OL, Bill, and N6DHZ, James, have Web pages that are good references for how many IRCs or greennstamps ($) to send.
Over the years the IRC has been modified or updated and yes even gone up in price. The current IRC is called the Doha model. This IRC is not available in the US, UK and other countries and has been available for purchase since the July 2013 time frame. These IRCs are valid through December 31, 2017.
This is the current Doha model International Reply Coupon (IRC), which is good through December 31, 2017.
If you have any of these old IRCs they should not be sent to any QSL managers and can not be redeemed at any Post Office. You may be able to sell them to a collector otherwise they are worthless.