Which iconic album was the first to feature a functional zipper as part of its vinyl record packaging design?

The music industry has seen numerous packaging innovations over the decades that have helped albums stand out on retail shelves and become collector's items. Some packaging designs have become nearly as iconic as the music itself, creating memorable unboxing experiences and adding value beyond the audio content. Test your knowledge about a groundbreaking album packaging innovation that changed how physical music products were marketed and perceived.

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The Rolling Stones' 'Sticky Fingers' (1971)
Led Zeppelin's 'Physical Graffiti' (1975)
Pink Floyd's 'The Dark Side of the Moon' (1973)
The Beatles' 'Sgt. Pepper's Lonely Hearts Club Band' (1967)