Very popular stainless steel from Hitachi. Many Sakai knifesmith will have some sort of ginsanko offerings. Working HRC is between 60 to 62, I consider Ginsan to be the stainless equivalent of White 2 steel.
This particular stock is in Sanmai constuction, namely it come with a Ginsan core and cladded with soft stainless steel, in a 3 layer constuction. This means the knife will be much easier to sharpen after heat treatment and when the user needs to thin the knife, it could be done with a whetstone rather than have to use a machine (which is not that practical, this is one of the reasons that I am not a big fan of PM monosteel knives).
Measurement: 360mm x 55mm x 2.5mm