Apollo-Soyuz Postal Cover Lot of 100 - 1975 NASA Mission EnvelopesThis wholesale offering includes 100 envelopes featuring a colorful cachet for this joint space mission by the United States and Russia. These are first day covers for USPS postage stamps released on July 15, 1975 to commemorate the launch. These are fun collectibles because they are uniquely tied to the original space event date through their postmark and thus can never be produced again. Collecting postal covers provides a route for learning more