Little about Asano Mikawa Shiro Nagura
They are from Junmikawashiro minein Aichi prefecture:
There are 4 stratas
from finest to coarsest
Koma, Mejiro, Tenjyou, Botan
コマ ( 細 ) 、目白 ( めじろ ), 天上 ( てんじょう ) 、ボタン、
And 4 grades (colours)
Superior high grade, High grade, Superior selected grade, Superior grade
特級上、特級、別上、上級
特級上、特級、別上、上級
Koma is most fine in grit but Botan, Tenjyou and Mejiri is fine too and its not much difference for knife sharpening
Honing a Kamisori with Asano Naguras, Iwasaki, Nakayama