What's so special about an unlabeled cassette?
Well, this particular one could be considered The Holy Grail by Al fans: it's the tape Al sent to Dr. Demento with "Belvedere Cruisin'," the first song of Al's that the Doctor ever played, making its debut on March 14, 1976!
It was received unmarked, just as it appears in the top photo, and with the apparent foresight to help preserve this important piece of history in Dementia, the Doctor labeled only the flip side (see bottom photo.) Note the other tracks which never received airplay: "Dr. D Superstar" - a parody of "Jesus Christ Superstar" dedicated to Dr. Demento. There are also station identification promos for KMET-FM, which broadcast the Dr. Demento Show live in Los Angeles from the early '70s through the late '80s.
Special thanks to Dr. Demento for the loan of the cassette for this page!