Appears to be the archive page that my search had missed;
another site offers the same file with link-back to Apple's:
From 2001, details include:
Download
File Size: 1263 Kb
archive link via pure-mac.com
"...The Power Mac G4 Firmware Update 4.2.8 will run only on Power Mac G4 and Macintosh Server G4 models with
AGP graphics running Mac OS 9.1 or later from a local hard disk. If you are using Mac OS X on your Power Mac G4 or
Macintosh Server G4, you must start up from a local Mac OS 9.1 or later writeable partition (not a CD or network disk)
before following the update instructions. Firmware Update 4.2.8 includes improvements to starting up Mac OS X from
the local hard disk, FireWire target disk mode, network startup, gigabit networking (on systems with gigabit hardware),
and system stability. This update also adds support for additional security options that allow the Open Firmware to be
password-protected..."
..from mactracker specification app..
Introduced January 2001
Discontinued July 2001
Model Identifier PowerMac3,4
Model Number M7627, M7688, M7945, M7681
EMC 1862
Order Number M7627LL/A (466 MHz), M7688LL/A (533 MHz), M8451LL/A, M7681LL/A (733 MHz)
So you likely have the correct if not only Firmware Update for the vintage cited.
Thank you for verifying the firmware version in an original archive source.
In any event...
