Disambiguation: Pre-Crisis Earth-Two / Earth-X, Eel O'Brian
Universe: DC : Earth-Two (Pre-Crisis)
First published in: 1973
Plastic Man of Earth-Two / Earth-X first appeared in Justice League of America (DC, 1960 series) #107 (September-October 1973).
See also the Mainstream Universe Plastic Man and Plastic Man of Pre-Crisis Earth-Twelve.
Link: https://en.wikipedia.org/wiki/Plastic_Man