Hi Guest, I don't have the LP you mention but I do remember some talk about it. Dominic was under contract at various times to various companies and using fictitious names was a way around that. While I was checking on my LPs of Dominic I came across one he made for Major Minor which had the Old Triangle. The credits read Arranged D. Behan, proof that he didn't write it. In those days (and now even) if a title was traditional, no money was paid to the writer obviously and the record company normally never paid out. The singer, by claiming the song was Trad. Arr. by him/her then received a royalty.
If you tell me the names of the "unknown" singer it could be a clue as to the identity as I know all Dom's pseudonyms.