Not to stir the pot too much on this subject, James, but the book does say:

Copyright C 2000 by James Campiglia & Steve Wells

I guess it's possible that your contract conveys ownership of the copyright to Schiffer, though.

My opinion is that using your grading method is no different from me using a catalog number from The Chip Rack to sell a chip I own. I would think that any chip owner or even a grading service would be able to use your criteria and grading scale as long as they mention where it was first defined.