Other mistake: At or just after the point where Steve McQueen restrains the diner owner from running out the door - McQueen's wedding ring is visible on his left hand throughout one entire long-shot. (He was 27, despite playing a teenager, and had been married to Neile Adams for more than a year).
The Blob (1958)
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Directed by: Irvin S. Yeaworth Jr., Russell S. Doughten Jr.
Starring: Steve McQueen, Aneta Corsaut, Earl Rowe, Olin Howland
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More mistakes in The Blob
Steve Andrews: How do you get people to protect themselves from something they don't believe in?
Question: The movie was made in 1958, why does the calendar in police station show July 1957?
Answer: Because movies aren't always set in the year they're released. Absent any conflicting information, the assumption must be that the events of the movie take place around July 1957.