MPO is an acronym for "Moulages Plastiques de l'Ouest" (in English: Western Plastics Castings).
MPO pressed its first commercial CD on 4th of December, 1984.
Vinyl discs pressed by MPO can be identified by the hand etched "MPO" etching in the runouts.
MPO can be credited as M.P.O. on releases.
MPO CDs made at Averton are assigned the following SID codes:
Mastering: L031, L032, L033, L035, L036, L039.
MPO isn't always explicitly mentioned in the CD matrix, but can sometimes be identified by a string of tiny text with the following format:
CA [label cat#] @@ IFPI LV88 M/D/YYYY HH:MM:SS [AM/PM] NNNNNNNNNN
If you aren't sure, please ask in the forums.