Vintage AOTO Japanese Natural Sharpening Stone 1904g (4lb. 3.2oz.)
215mmX63mmX59mm
It still comes with an original box and a tag by Asahitoro, Matsunaga Stone Co. Ltd.
In general speaking, Aoto is medium to medium high grit stone.
It is heavy condensed stone, and it looks what it is medium-high grit to entry class fine grit stone.
It is an old days Aoto whetstone.
Hardness-------------8.2
It raises very good enough amount of slurry for sharpening quickly, and it is not too soft.
it is middle range hardness Aoto.
(Scale; 1 to 10, 1-3 is very soft muddy rough grit whetstone 3-6 is soft medium grit whetstone, 6-8 is hard medium grit whetstone, 8-10 is fine grit whetstone)
Particle Size---------7.6
(Scale; 1 to 10, 1-3 give deep scratch marks to the steel, 3-5 is delete the 1-3 scratches, 5-8 makes the steel cloudy, 8-10 makes the steel semi-mirror finish or mirror finish)
My white I steel blade knife Jigane became dark frosted silver color, and Hagane became from bright silver color finish.
It was from used market here in Hawaii.
Hawaii has a long immigrant history from Japan (I guess it has been about 160 years), so Carpenter, barber, cook, fish cutter, butcher, etc. needed good sharpening stones, especially carpenter and barber needed high-quality fine grit stones in old days.