Exactly 50 years ago today, Led Zeppelin released their iconic fourth studio album Led Zeppelin 4.

However, the album is technically an untitled album. The band was becoming so frustrated from critics’ negative reviews of their music, so Jimmy Page convinced Led Zeppelin to keep the album as anonymous as possible, with little evidence of who’s album it really was. Instead of including the name “Led Zeppelin” on the album cover, four symbols were featured that represented each member of the band.

Watch Led Zeppelin perform Stairway To Heaven from Led Zeppelin IV here: