: Represents the internal revision version of the BIOS used by Sony. The 'a' indicates it is for North American (NTSC-U/C) console models 1.2.6 .
This specific BIOS version was shipped with later revisions of the "fat" PlayStation 2 consoles. Specifically, it is associated with the (often referred to as the "v9" or "v10" motherboard revisions). ps2-0200a-20040614