This is an 8-sun double-edged saw made by Sadagoro Nakaya. A blacksmith praised as first-rate by Nagakatsu, a master of saw sharpening. The straightening is also, as expected, first-rate. Sadagoro is a disciple of the 5th generation Inosuke. The younger brother of the 2nd generation Inosuke is the famous Sadasuke Shibuki. The explanation will be long, so please search for more information. I also use this saw on site. A hard-to-find saw. Thank you.