This tanto is from the koto era and is what is know as a yoroidoshi or armor piercing blade. This design is for stabbing thru armor or chain mail.  That is why it is so thick and short.  The sword is signed hiromitsu and many smiths used this name so it is difficult to narrow down the smith without shinsa.  This blade has good work in the hada and hamon and comes with good mounts that are original and not newly restored.  This tanto has not been submitted to shinsa so it is being sold in the original condition as it was when brought back from Japan after WWII.