Justice League of America #209

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The heroes triumphantly defeat Per Degaton on Earth-2 in 1942 (reverting him to a lowly lab assistant to Prof. Zee in 1947, remembering the events he caused as only another dream), as well as the Crime Syndicate (returning them to their limbo prison in the Earth-3 universe), returning things to normal on both Earth-2 in 1982 and Earth-Prime circa 1962 (with all forgetting this adventure ever happened).