Probably an airing expiry, rather than disc expiry. Unless, of course, it's a lacquer transcription disc.
Yep, that would be an airing expiry. I'm suspecting that this was sent by the Beeb to an 'affiliated' station down under for airplay. Back in 1971 the old Colonial links (including cultural) were a bit stronger than today.
On a similar subject, one of these transcriptions recorded by Tubby Hayes' Quartet, as recorded for broadcast in Spain, was issued by Harkitt a few years ago ('Commonwealth Blues' I think). That one was in (decent) mono.