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Well technically....the 1957 film version of 12AM. The original was a 1953 TV play the tape of which is now lost.
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Actually it was 1954, and a kinescope was recently discovered. I don't know if it's available for public viewing yet.
TAM was deinitely Fiedler's best role, and he has one of the film's greatest moments, finally standing up to blowhard Lee J. Cobb: "You said we could throw out all the other evidence!"