Dear Haris,
Two-ish, then. Grades aren't all that fixed: ISO(R) numbers are much more reliable, and refer to the log brightness range required to give a full range on the paper. Really hard papers (grade 5 graded) are maybe ISO(R) 40-45 (log range 0.40-0.45), while really soft ones (grade 00 Multigrade) might be ISO(R) 160 or more (log range 1.6 or more). 'Grade 2' is typically anything from 90 to 110. Some papers have become harder over the years, i.e. a grade 3 that was 100 might now be 90.
Cheers,
Roger