[Arkasha]

Beats me. I've got several references that indicate no filters are required to achieve grade 2.

Edit - checked out this Ilford informational pdf - http://www.ilfordphoto.com/Webfiles/...0201152306.pdf - and it also reads "0" filtration for G2.

See the "single colour filter settings" table. I can see where you claim filters are used, but I think that's in the case where the user wants to not have to change exposure times with grades.