It's B, then for an 81 car it's B1, 82 car it's B2, 83 car B3 etc etc....
Special Black is A, an 81 car is A1, my 89 is A9, etc etc.



Just to ilustrate how the system works, hope that helps. If you ask for "diamond white" at a paint place they'll do you B1, the 81 shade.