There were 86 stories in the first eleven Superman reprint collections. All but eleven were originally published from 1957 to 1961. The oldest story dated from 1952. Then in 80 Page Giant G18 three stories from 1942 and 1944 were reprinted. I can remember being astonished by how different they were from the stories I was used to - an unrecognizable Superman, Lois Lane and Metropolis. The stories also turned out to be among the best of the early ones.
At the time I didn't know that one of the stories was significantly altered. Originally published in Superman 19 (Nov-Dec 1942) as "Superman, Matinee Idol!" the title was changed to "Superman, Cartoon Hero!" when reprinted. The introduction was changed and "Our First Imaginary Story" added. The second page has a telling change. The co-creators names have been removed from the cartoon's credits. In 1966 they were non-persons as far as DC Comics was concerned. It wasn't until the 1970s that the company was compelled to add their names to all Superman stories. Finally a nine panel sequence near the end of the story was removed and the last panel before the cut sequence has been changed. The original pages below are from the reprint in Superman Archives Volume Five (New York: DC Comics, 2000).