CBS/Sony opened the first commercial CD pressing plant in Japan in 1982.  In the early days of the CD, many record labels turned to CBS/Sony to press their discs.  As a way to track the many manufacturing projects in the plant, for both outside labels and their own, CBS/Sony developed a system of project identification codes.  These codes appeared on discs and inserts for many titles issued outside of Japan.  Additionally, this system was later applied to discs coming out of CBS/Sony’s Digital Audio Disc Corp. (DADC) plant in the U.S.  Common project identification codes with their definitions and/or uses are as follows:

• saturday delivery on soma DIDP: Digital Identification Project; DIDP numbers were used on CBS/Sony rock, pop, and jazz titles.
• DIDC: Digital Identification Classical; DIDC numbers were used on CBS/Sony classical titles.
• DIDX: Digital Identification External; DIDX numbers were used on non-CBS/Sony titles.
• DIDZ: The definition of the ‘Z’ is unknown, but DIDZ numbers were used on non-CBS/Sony titles as an alternative to DIDX numbers.
• DIDY: The definition of the ‘Y’ is unknown, but DIDY numbers were used on Columbia Record Club mail-order issues.

For the most part, a non-CBS/Sony title was assigned either a DIDX or a DIDZ number.  However, certain early A&M titles released in the U.S. were issued both numbers.  Discs are not found with both numbers.  Rather, two different issues exist, one with a DIDX number and one with a DIDZ number.  Both discs were pressed by CBS/Sony in Japan, and the discs and inserts are very similar in appearance.  The DIDX or DIDZ number appears on both the disc and the inserts.  It is presumed that the DIDZ discs were pressed first because the inserts in most cases were printed in Japan, whereas inserts with the DIDX discs were printed in the U.S.

Shown below are two early U.S. issues of Supertramp Breakfast in America with catalog number CD-3708.  Both discs were pressed by CBS/Sony and have “CSR COMPACT DISC” repeating in the plastic ring.  The top disc bears “DIDZ 10078” beneath the catalog number, and the matrix code is “DIDZ-10078 11”.  The bottom disc bears “DIDX-26” beneath the catalog number, and the matrix code is “DIDX-26 21”.  It is not clear to me why both issues exist.  As stated above, both are early U.S. issues.  There is no information on the inserts to suggest different distribution channels for the two discs.

Other A&M titles that exist as Japanese CBS/Sony DIDX and DIDZ pressings are Supertramp Crime of the Century (DIDX 25 and DIDZ 10076), The Police Ghost in the Machine (DIDX 2 and DIDZ 10070) and Synchronicity (DIDX 1 and DIDZ 10057), and Herb Alpert Rise (DIDX 3 and DIDZ 10074).  In my experience, both pressings for these titles and for Breakfast in America are quite rare.