Just a quick addition to what Scour said:
The media code is not a guarenteed way of knowing the manufacturer of the media. Many companies use other companies' codes for their own media, sometimes with permission and sometimes without. For instance, Prodisc and CMC both use MCC's code for their media on occasion, with the permission of MCC. Other companies, like Princo, are known to use other companies' codes pretty much whenever they feel like it, without any permission.
In other situations, companies make the stamper used to create the blank media, but let another larger plant use that stamper to make media for them. An instance of this would be Fuji who makes stampers for their own media, but gets Prodisc to do the actual pressing of the discs.
Situations like this make it very hard to know the real manufacturer, or all the situations involved in the making of a disc, just by the media code alone! Although the media code is a good start
Punch Cards -> Paper Tape -> Tape Drive -> 8" Floppy Diskette -> 5 1/4" Floppy Diskette -> 3 1/2" "Flippy" Diskette -> CD-R -> DVD±R -> BD-R
The Progression of Computer Media