You may be able to use Software Update to determine the correct
firmware update for the new USB aluminum keyboard. If you are
not familiar with the process, the links about the two different
firmware updates have some information, and also the download
items themselves will also have more.
And in Software Update re:
http://www.apple.com/softwareupdate/
you can see the version number of an update and then use the
correct stand-alone link (such as those given for USB keyboard)
as posted above, to get the same update as a separate download.
You should not need to get the item separate from Software Update.
The newly acquired keyboard may be able to tell you what the
current as-shipped firmware version is, by using the System
Profiler in your computer when attached to the keyboard, and
see under the hardware (USB) if the product info given shows
this new keyboard's firmware version; or a reference to it.
And since the new keyboard supports OS X 10.4.10 to 10.5.x
any keyboard shortcuts and settings in the keyboard preference
panel, as well as any which appear in the Keyboard Viewer,
naturally should be available to you. There may be some regional
differences in what characters are available, depending on your
language choice(s) and the keyboard type you own, if not english.
Plus, there are many standard Mac keyboard combinations to use.
Hopefully all these words will be of help...
Good luck & happy computing! 🙂