Ya, it was definitely caked with crud, and so I couldn't see the square 3/8 drive hole. I found it by accident shortly after posting this. Thanks for all help!
-Gl@dius-
PS. Also shortly after, I (while thinking purposefully about NOT doing it) stuck my hand under the idling blade, I got 9 stitches in one finger, 3 in the other, I'm lucky to have them at all. call me absent-minded...
Philip Knowlton, March 2008