The cassette holder is visible in the video. There is writing in white-out on the cassette, which labels one side "Bad Radio", and the other side "The Butts". A written note inside the cassette says "this is the butts first demo. must see live. keep in touch. eddie (phone #)"
If these three tracks are indeed The Butts and not Bad Radio, then I believe it will be the earliest known recordings from Eddie Vedder."
Download "Plenty Of Time" song
(as 320kbps mp3; I removed the gaps within the song)
Listen it's original post on youtube