Quote from Rydian;1282496:
IIRC "grades" are just player-given terms. The actual stat is "quality", which every item can optionally have.
http://mabination.com/threads/85245-Player-made-Item-Quality
However we don't know what quality translated to which stats for wands and staves since those weren't craftable back when, and it'll need to be logged and tested a lot by people who can make them now.
Grades are essentially quality but less precise. This is actually a new thing tbh, as magic craft/engineering weapons
can come with a quality on them, but it has little to no bearing on the item's stats, or so I had thought.
Items dropped from Girgashiy Raids have quality on them, generally around 70~80. I cataloged quite a few of them from various runs (about a dozen different weapons), but haven't really been on the ball about it lately or done much testing on it.