This stone I bought from an auction at 330mate.com. I have gotten a lot of stones from them in wholesale batches at very low prices. Some stones have been really bad and some merely mediocre, but a few have become good and even excellent stones after a bit of work with my trusty #140 diamond plate grinding trough the dirty layers on the search for a clean board. A couple of the stones I have gotten from 330mate have been real bargains. Some of the better stones are sold at their Dutch auction, but you can take even more of the uncertainty out of the equation by requesting a specific stone from them, as I did with the 130x85x33mm Nakayama koppa, but then you will have to fork up a lot more money for their efforts selecting a good quality stone for you. That said, I kind of enjoy buying batches of low priced ugly looking stones from 330mate, searching for that one jewel to be found. It has happened to me a couple of times, and it is a very exciting feeling when it happens.
As you can see from this close up, the scratch pattern from the stone is very fine and homogenous. However it makes only a slight contrast between the Ji and Ha. This shows that the stone polishes both Hagane and Jigane equally well.
From the reflection picture, you can easily see the exeptionally fine finish this stone puts on the knife. This polished look is actually due to a very fine and complex scratch pattern from the natural stone. Looking at the close up picture above, the surface is actually matte or hazy to the look. This highly complex scratch pattern I believe is one of the main factors to get the edge really sharp and more wear resistant than an edge polished to a full mirror finish by fine synthetic abrasives. You can find some very good reading about this theory here http://thejapanblade.com/sharpvsshiny.htm. I can easily shave with any high carbon steel edge coming off this stone.
This stone is one of the best bargains I have made from 330mate. A really amazing stone at a very, very reasonable price.