Used stamps exchanges.
You send 25 used stamps
to a random member
and you receive 25 back!
25stamps.club offers a compact way to exchange used postage stamps with collectors around the world. Members send 25 different stamps in good condition to a randomly assigned partner and include the exchange ID in the envelope. When the recipient registers the delivery, the sender can receive a lot of 25 used stamps from another member. It is a simple format for discovering stamps through real mail.