On the surface this cassette release gives the appearance of being a straight repacking and reissue of the 1972 album of the same name, which itself appeared on cassette in 1975 (with several additional tracks included in this repackage). The cassette was released alongside another vinyl album of the same name and catalogue number in June 1978 on the Encore record label (a subsidiary belonging to EMI) in stereo with the catalogue number TC-ONCR502. See the appropriate page for that album for full track change information.
This design of cassette shell was introduced in early 1977 and was produced in both grey (as in this image) and cream coloured plastic. The text was printed directly onto the cassette body in blue (as in this image), red or black ink. As can be seen on the images the tape was produced with the Dolby noise reduction system to improve the quality of the sound when played on suitable players (noticeably to reduce the hiss associated with tape playback).
This album release appears to be only found in the grey shell with blue text.
This style of cassette case insert was introduced by EMI in 1978. It was printed by Garrod & Lofthouse (who also produced the vinyl album sleeve) in June 1978 as indicated by the line 7806 G&L. The idea was to have a full height cover which kept the original concept design of the vinyl album release and the addition of a coloured band across the top. In the case of this Adge Cutler release the artwork was maintained and the album title and group's name put onto a light blue band. The Encore and EMI logos were superimposed over the artwork.
Beneath the catalogue number TC-ONCR 502 appears another code number OC 254-06 680. Between 1969 and 1982 EMI had an international coding system which they hoped would get adopted industry wide, and they used it worldwide for their own releases. In fact, the numbers used formed the basis of the 7-digit numbers adopted in 1983 and inserted into EAN/UPC barcode-based cataloguing, used to this day.