233 iMac firmware problem

I've bought a second-hand bondi blue 233 iMac, for my daughter. It came with OS8, and I've installed OSX. It runs fine, except it has to be booted up with the "mac-boot" command. I realise now that I should have installed OS9 first, but it's too late now! I've read up about firmware updates, etc, but how do I know which one is currently installed and which update is the correct one? Also, how do I tell if the iMac is a "Rev B"?

Mark Dawson, Jersey, Channel Islands