Rescued from a corrupted hard drive by: unstattedCommoner
The author writes:
However, on this occasion the proper conclusion is that the author screwed up but couldn't be bothered to correct the error, notwithstanding that they foresaw that they would consequently be deluged by messages pointing out the error from people who didn't bother to read this annotation. It was indeed the Old Etonians who won the FA Cup in 1882, so the answer to the second question should be "No".
UPDATE: Apparently you all read the annotation. Well done.
UPDATE #2: Except for the 33 of you who are (re-)reading the strip five years after it was first published.