I know this is a while ago, and it coulda trivially been verified by google and wikipedia, but i finally came across the Annotated Casey at the Bat on the shelves again.
In front of version 1 is the following paragraph:
"THIS is the original version of Casey--word for word, comma for comma--exactly as it appeared in the fourth column of the San Francisco Examiner, Sunday morning, June 3, 1888."
(I don't entirely believe it, as there are lots of little numbers referring to notes on later pages, but i bet in this case, that's what "annotated" means...)
Of further interest, it appears version 25 is "Cool" Casey at the Bat, by the editors of Mad, originally published in October '60.