You can have 4 Table Grades in Williams Pinball. Depending on these, you can access different features on your pinball tables.
Grade 1:
Unlocks Basic Challenge
Grade 2:
Unlocks Arcade Play. Advanced Challenge, Ball Skins, Offline Play
Grade 3:
Unlocks Pro Challenge, Flipper Skins, Visual Extras
Grade 4:
Unlocks Save Game, Ball Trails, Pro Difficulty, Pro Physics, Practice Play