Well we're currently (as of today) on the 3rd revision of the G4 ibooks, before that there were 900 Mhz G3 ibooks, so that one must be around 1 revision before that.
A wild guess would be end of 2002/beginning 2003...
"how do you that? i heard that apple site has the guide"
The documentation has a guide, but it really couldn't be simpler...
There are 3 latches: 1 next to the esc key, one next to the F12 key. The other is actually a screwed latch that doubles as a num key indicator.
Just screw the num key latch, and pull down the other 2 latches and you can lift up the keyboard - Careful, it's still attached to the 'book by a ribbon cable, don't break that!!!
Underneath is the airport card slot, just stick it in, attach the antenna (also right there) close it up and you're done!