What version of OS X? It it written in the smaller text on the left bottom of the disc.. It should say Mac OS version 10.3, 10.3.3, 10.3.4, 10.3.5, 10.3.7, 10.4.2, or 10.4.4. Also has the AHT (Apple Hardware Test) version, Disc version, and a part number. These number are critical for determining which iBook G4 they are compatible with.