Major and minor version fields are the main variants between version of 6.x (The last two bytes in this signature). The signature follows the pattern of: BOF Byte 0 = FF, Bytes 1-3 = WPC, Bytes 4-7 = size of header, Byte 8 = Product, Byte 9 = FileType, Byte 10 = Major version, Byte 11= Minor Version, Bytes 12-13 = Encryption, Bytes 14-15 = Unused (0).