All my music CDs from Japan have a code printed on the back (and sometimes also on the disk or the booklet). It seems to start with capitalized letters and to end with numerals.
For example, my soundtrack to the movie Oldboy has EKLD 0307
and my soundtrack to the anime Wolf’s Rain has LC 01666
.
What is the meaning of this code? Does it identify the release, the disk, the work, or something else?