Unofficial US RSD Release. 50-year anniversary vinyl release of the original power trio's second incarnation, now expanded with BBC In Concert versions of the album's key tracks. An epic milestone and key prog rock definer, fusing their blues rock roots and their finely honed electric sound of the early '70s. This limited release replicated the original 1971 packaging, with a tri-fold sleeve, an absolute essential for fans of this seminal act.