Something else I would like to ask, and I think it is somehow important, if the Imanishi labels have a meaning.
On their stamp about the stone's grade, like the link from Dave http://www.thebestthings.com/newtool...ne_atago_1.jpg (thanks Dave, I discovered it with your help) I have seen two stamps; the 一本線 and the XXX品 (I can't read these handwritten like "fluid" kanji, not even find them by radicals).
The stones with the 一本線 grade label are from 20% to higher than 50% more expensive than the stones with the XXX品 stamp (the link above has it).
So, is there a difference between them? They appear to be taking it seriously.

Also, Ohira is a western mine stone? I thought it was an eastern mine stone. Anyway, I don't think the classification is that important.
So Jnat-san, you think that the stones advertised as Atago, aside from finishing qualities, are not fast enough generally?