The 1928 cartoon "Sleigh Bells" featuring Oswald the Lucky Rabbit had been hiding in plain sight in the BFI National Archive and was re-discovered by a researcher browsing the online catalogue.
It wasn't as simple as seeing the cartoon's title and knowing that it was the missing Disney film.
"There must be a hundred things called 'Sleigh Bells,'" a BFI spokesman told The Guardian.
Once the print was verified, however, Walt Disney Animation Studios supervised the cartoon's restoration and created a new print for preservation as well as digital copies, BFI said in a news release.
"The restoration of this film will introduce many audiences to Disney’s work in the silent period," Robin Baker, head curator of the BFI National Archive, said in the release. "It clearly demonstrates the vitality and imagination of his animation at a key point in his early career."
The restored cartoon will be shown for the first time in 87 years next month in London, but a short clip of the film is available on the BFI website now.
Last year, a print of another lost "Oswald" cartoon was found in the National Library of Norway.
"The Oswald shorts are an important part of our Studios’ history, and we have been working with film archives and private collectors all around the world to research the missing titles," Andrew Millstein, president of Walt Disney Animation Studios, said in a statement.
Oswald the Lucky Rabbit was created by Disney and animator Ub Iwerks for Universal. They produced 26 "Oswald" cartoons, but lost the rights to the character in a contract dispute with the studio. Universal continued to produce "Oswald" cartoons while Disney and Iwerks went on to create Mickey Mouse.
The Walt Disney Company regained the rights to Oswald in a unique trade: The company allowed sportscaster Al Michaels, who worked at Disney-owned ABC, to leave for Universal-owned NBC in exchange for Oswald.
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