Mark,
MD> Mac OS X puts a different signature there than does Mac OS 8/9. And if MD> we ever make any significant changes in the part of the code that MD> handles the on-disk structures, we will probably use yet another MD> signature. Older versions of Disk Doctor complained about the Mac OS X MD> signature, but current versions don't seem to.
On my older 6100, under 8.1, I get "8.10". On my new eMac under OS X, I get "10.0". I still have to upgrade it to Jaguar and will see what gives.