Made in Japan.
Over time, any sharpening stone will start to wear and the surface will become hollowed out somewhat, and so it will need to be flattened (also sometimes referred to dressing). This stone is made for this purpose. You can wet the surface and rub the stone gently over the top, taking off the high edges and making the stone flat again. You can also spread a small amount of silicon carbide "sand" on the sharpening stone to help the grinding and smoothing. This is a very large and heavy stone so it's useful for even pretty large stones such as the Chosera, and includes rubber bumbers for the ends to help steady it while in use.