This tending towards green Okudo asagi stone, graded in Japan by size, is considered to be a size #35. It is (205 long x 73mm wide x 27mm thick). A carpenter's stone for chisels, plane blades, or large knives. It will act as a stone for razors in a professional shop, but this size is unnecessarily large.  
 
Japanese writing on the stone, Shohonyama, nogiku (wild chrysanthemum), Saikokyu (very best quality}
 
 
 
 
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