This appears to be a compilation of recordings originally released on Tribune Records,
unsurprising given that Plough was essentially the successor of Tribune Records,
and would have access to the same masters.
However, without more details about the recordings and without comparing the tracks
side by side, I cannot be certain of this claim.
Possible sources:
A2, A5, A6 and B2 were probably taken from the Live At The Embankment LP [1967] ¹.
A4, B4 and B5 probably from Ballads for Drinking and the Crack [1968] ².
A1 and B1 were originally released on the same single in 1969 (Tribune TRS 136).
It seems likely the remaining 3 tracks (A3, B3, B6) are also from Tribune releases.