Next album to this one is the Chitty Chitty Bang Bang soundtrack on United Artists Records.
The number may vary from 5048 to 6048. This is due to the Estereo kind. Originally, EMI suppliers made a difference between mono and stereo by the first number. 5XXX for mono and 6XXX for Stereo. In the 70s this system was drop and it was started to being used the “S” prefix for stereo.
Notice that the number is consecutive, but no the X letter.
Indeed, this IS an Official album.
Opus in Argentina was the label that distribute Vogue recordings here.
I don’t know the reasons why it was catalogued or label as “unofficial”
Something to comment on the first photos.
The photos I posted is a repressing of 1976. This can be determined by the Sicamericana S.A.C.I.F.I. address on label, and the AADI-CAPIF and SADAIC-BIEM collective entities.