A long-lost Orson Welles film that was feared to have been destroyed in a fire in 1970 has been discovered in a northern Italian warehouse and will finally make its public debut 75 years after being filmed, an Italian film archive has announced.

The silent film, Too Much Johnson, a slapstick comedy made just before Welles went to Hollywood to film Citizen Kane, was found in a box that had been stored for years in the northeastern city of Pordenone before being identified, said Giuliana Puppin, spokeswoman for the Cineteca del Friuli archive.

How the 35mm nitrate print arrived in Pordenone remains a mystery.

Found by a shipping company, it was turned over at some point to a local film society – but the film seemed of no particular value and was left unopened for many years, Puppin said.

“We don’t know where the box came from. There were no documents with it. We don’t know the road it took,” she said.

Too Much Johnson stars Joseph Cotton and is not so much a feature film as a series of scenes made to be shown as part of a production of the play by the same name, said Circo Giorgini, an Italian expert on Welles who identified the film about three years ago. It was never finished and never shown publicly.

While the existence of the film was known, the only remaining copy was believed to have been destroyed in a 1970 fire at Welles’s home in Madrid, Spain. It is not known how many copies of the film were actually made.

Giorgini said he knew immediately that Too Much Johnson had been found when he got a call from a friend saying he believed he was in possession of a Welles film that starred Cotton wearing a straw hat – the give-away.

“I said: ‘It is something very precious, take care of it. You have found a film that has been missing for decades’,” Giorgini said.

The expert said actually viewing the film “was like finding an important, lost painting – like seeing a painting of Caravaggio that no one knew about.

“This movie shows that Welles, still younger than we knew, at the age of 20, was demonstrating a great talent and great mastery of cinema. It would be confirmed a few years later with Citizen Kane,” he said.

Giorgini, who made a 1993 documentary about Welles, said he believes the film was left behind when Welles bolted from Italy, where he had been living, after a gossip magazine reported that he was having an affair while married to his third wife, Paola Mori.

“He was very protective of his private life, and he packed his bags and left within a week. As far as I know, he never returned to Italy,” Giorgini said.

The film has been newly restored by George Eastman House in Rochester, New York, with funding by the National Film Preservation Foundation in San Francisco. It will debut at Le Giornate del Cinema Muto, a silent film festival in Pordenone, on October 9.