The celluloid of the German classic was in private hands for 80 years and then was in the Museum of Cinema in Buenos Aires where it was discovered in April with never before seen scratched images.

Museum director Paula Felix-Didier said theirs is the only copy of German director Fritz Lang's complete film.

Three reels, edited out and long thought lost, were part of the discovery of the film that depicts a 21st century world divided between an underworld working class and the above-ground thinkers who control them.

Buenos Aires film distributor Adolfo Z. Wilson acquired a long version of "Metropolis" in 1928 which survived as a copy, and finally ended up in the archive of a local film museum, said Felix-Didier.

Rediscovered reels deemed authentic

A DVD of the version was brought to the Friedrich Wilhelm Murnau Foundation in Wiesbaden, Germany, for analysis. Researchers at the foundation, which owns the rights to "Metropolis," confirmed that the scenes were original.

"We were overjoyed when we heard about the find," foundation head Helmut Possmann told Reuters news agency. "We no longer believed we'd see this. Time and again we had had calls about supposed footage but were disappointed.

"We're not being fooled," he said. "The film can now be shown more or less as Lang originally intended it. In terms of understanding what it's about, we'll be seeing a new film."

Material expands characters and plot

Around 20 to 25 minutes of footage that fleshes out secondary characters and sheds light on the plot would be added to the film pending restoration, he added. But around five minutes of the original were probably still missing, he said.

Due to the poor condition of the film stock, it was too early to say how long restoration would take, Possmann said.

"It's taken several years with similar films," he added.

Written by Lang and his actress wife Thea von Harbou, “Metropolis” was originally three-and-a-half-hours long but was cut into a shorter version since seen by millions worldwide.

Commercial flop to influential blueprint

It was not a commercial success and nearly bankrupted the studio behind it. According to some estimates, it still ranks as one of the most expensive movies ever made once inflation is factored in.

With its cold, monumental vision of a vast mechanized society in the middle of a tumultuous class struggle, "Metropolis" forged a template for generations of science fiction cinema, and its enduring influence has been cited on films from "Blade Runner" to "Fahrenheit 451" and "Star Wars."

"Metropolis," was the first film to be entered into UNESCO's Memory of the World Register -- which aims to preserve cultural achievements of outstanding significance.