Hi, Martin - I got a reply from Bob Waltz of the Traditional Ballad Index. Here's what he says.
-Joe Offer-

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Joe: Hi, Bob - somebody at the Mudcat Cafe pointed out a possible error on your information on "Skibbereen." You show the "earliest date" as 1062, and he's sure it's not that. Got any idea what that date is?

Oh, it's obvious. I know my typos. :-) It's 1962.

Now we both know the song is older than that. But that date (Galvin's
publication) is as early as I can verify it, as Galvin gives no source.

The very fact that it shows up in Australia pretty well proves that
it's older. :-)

Thanks for catching that.