This stone is razor grade. The black kawa skin, cloudy appearance and manazu lines are all indicative of Namayama stones. The stone has goma or "sesame seeds" that don't scratch. If they aren't too hard, goma boosts cutting speed. The light dots are nashiji or "pear skin" and are also considered the mark of a high quality nakayama stone. This stone will work with razors, kitchen knives or woodworking tools.
The stone weighs 1 pound 14 ounces and the dimensions are about 7.5" x 2.5" x 1". Weight is 2 pounds, 6oz. We only get about 1 or 2 a year of the Nakayamas and this is an excellent example.