NEW YORK — A handwritten notebook by British World War II code-breaking genius Alan Turing is expected to bring at least $1 million at auction in New York.

The 56-page manuscript was written at the time the mathematician and computer science pioneer was working to break the seemingly unbreakable Enigma codes used by the Germans throughout the war. It contains Turing’s complex mathematical and computer science notations, and is believed to be the only extensive Turing manuscript known to exist, according to Bonhams.

The story of how Turing and a team of cryptanalysts broke the code was portrayed in the 2014 movie, “The Imitation Game,” starring Benedict Cumberbatch in the role of Turing.

The notebook dates from 1942, when they were at Britain’s World War II code and cypher school Bletchley Park. In one entry, Turing writes about a complex calculus notation.