We need to explain this, without actually knowing if our explanation is correct or not.  Voice of America during the 1960s and 1970s made every effort to engage its international listeners.  Coming at the same time as America’s space programme, it appears that VOA created a club (“Club de Oyentes … Unidos por la Verdad”) and issued membership cards.  So this otherwise unused postcard has astronauts on the front (code 36300030A), and some information in Spanish on the back, along with a plastic membership card taped on (code 36300030B).  We suppose any listener could just write in and join–a common practice for shortwave radio back then.  Strictly speaking this is not a QSL, but close enough.  Despite the aging tape, we will call this Grade: 1