noun
international reply coupon
A coupon exchangeable for postage stamps in any UPU member country, used to prepay return postage for international mail.
国際返信切手券を同封すれば、海外からの返信がもらいやすくなります。
If you enclose an international reply coupon, it will be easier to receive a reply from abroad.
Compound of 国際 (international), 返信 (reply), 切手 (stamp), and 券 (ticket/coupon).