Vintage AOTO Japanese Natural Sharpening Stone 2822g (6lb. 2.9oz.)
223mmX50-67mmX78mm
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 large size Aoto whetstone.
Hardness-------------8.7
It raises good enough amount of slurry for sharpening quickly, and it is hard 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--------- 7.8
(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 frosted silver color, and Hagane became from bright silver color finish to almost semi-mirror 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.
Natural whetstone has more wide capacity than artificial whetstone, and actually, we do not know until sharpen blade on the stone. Sometimes, treasure whetstone is found after used it for a while. Never know until then.