Classic Ohira red-renge filled suita. This stone as demonstrated by the shape and the display of kawa skin on all four sides is a nook stone, salvaged from a crevice in the mine that determined its width and shape. Oddly shaped but measured as 175 x 80 x 30mm thick.
I tested this stone with a vintage 1910s Wade & Butcher razor, a more modern Kikuhide #1050 razor, and a Swedish steel (Rockwell 65)  kanna blade by Ogata Shuji of Niigata. The Ogata blade was scratched indicating that this is a high grade stone that will hone even the hardest of steels. 
Included is a tomo-nagura slurry stone.