As noted on Discogs.com, the only place I could find any information on this record:
"Bootleg 7" released between 1988 and 1989. Sleeve states "Concept & Arrangement by Messenger & Dartnell". "The Slog" is a cut-up megamix filled with vocal and instrumental samples from many Led Zeppelin songs layered over the beat from "When The Levee Breaks".
"Black Dog" is an acoustic version of the song, but many Zeppelin experts debate whether or not it is an genuine outtake or a cover band performing it."
I would have to concur with that evaluation as I also do not believe the B-side as Led Zeppelin.