Nirvana artifacts and exhibits are seen at the opening of In Bloom: The Nirvana Exhibition, at a London art gallery on Sept. 13, 2011. The album’s 20th anniversary featured a $20 bill, but the original album had a $1 bill.

LONDON – SEPTEMBER 13: Nirvana artefacts and exhibits are seen at the opening of ‘In Bloom: The Nirvana Exhibition’, marking the 20th Anniversary of the release of Nirvana’s Nevermind album, at the Loading Bay Gallery on September 13, 2011 in London, England. (Photo by Samir Hussein/Getty Images)