I was curious what the IFPI serials that you see on CDs mean so I did a little research and thought I'd share the info.
Evidentally, IFPI stands for "International Federation of the Phonographic Industry".
IFPI numbers show the manufacturer of the disk as well as the serial for the specific machines used in the process. For instance, IFPI 5100 is on a lot of US PS1 games- the "51" is Sony's manufacturing code and the "00" is the serial for the machine used top press the disk.
To quote:
"SID codes supply the IDs of the machines used for the CD manufacturing:
The outer SID code IFPI Lxxx is the ID of the machine that procuded the CD master. So if two different codes exist, it just means that at least 2 CD masters have been manufactured, due to a large pressing amount of the CD.
The inner SID code IFPI xxxx is the ID of the machine in which the copy was pressed. CDs are often pressed in parallel by several machines, even for small pressing amounts."
Here's an IFPI# code chart (German).
Here's the article in Germenglish.