I have a few oes2sp3 boxes running on sles10sp3. One of these is my
SMT box, and a while ago (before reading sles10sp4 was not officially
supported for oes yet) I applied the "move-to-sles10-sp4" update
through the zmd service on that box.

That is the only sp4 'update' I've put on that box, and of course the
only updates it sees are sp4 related, which I've not applied.

Is there any way to revert back to sles10sp3 and have it show the
optional update to go to sp4 again?