12495 refers to the song by Patrick Galvin. Roud quotes two sources, one being Irish Songs of Resistance, where for some reason, Galvin doesn't acknowledge his own authorship. Given the lack of any evidence to the contrary, Steve probably assumed it was a traditional song and therefore catalogued it, along with all the other songs in the book.

The other source is a cassette which Comhaltas Ceoltoiri Eireann published under the title Traditional Songs & Singers. There it is performed by Liam Weldon. Let's not go down the road of what constitutes a traditional singer, but I would have described Weldon as a revivalist singer and songwriter. In any event, Steve was probably misled by the title, and by the inclusion of people like Elizabeth Cronin, Paddy Tunney and Geordie Hanna into thinking that the contents were precisely what it said on the label.