In 1990, excitement galore surrounded a "new" Zeppelin track coming out soon on some sort of box set.  It turned out to be "Travelling Riverside Blues", not new at all, but something the band did for the BBC back in 1969.  Contractual agreements were eventually made for it's release, now on the box set, the BBC album and the expanded version of Coda.  It's never on the air anymore which makes it perfect for the Vault!