On-sale date from copyright registration.
Inks credit by Bob Bailey. We previously credited George Klein.
Story done before John F. Kennedy's death. Originally intended for Superman (DC, 1939 series) #168 (April 1964), which would have been printed in January 1964 for a February 1964 release, but was pulled off the schedule when President Kennedy was assassinated in late November 1963. Published afterwards by request of President Johnson.
time travel story; NOT an imaginary story, despite cover blurb