This is a very old tanto from Japan dating to the Muromachi period in the 1500s. It features a faded hitatsura (little temper all over) hamon.
It was shortened from a longer blade at some point, possibly due to damage of the lower part.
The pitted yet smooth black patina on the tang hints at its age.
This blade may have been damaged by fire, as suggested by the streaks of martensite crystals on the surface. Alternatively, these martensite crystals could be a side effect of the scattered hitatsura hamon.
Not a very nice piece, but it holds quite a bit of history. Comes in an old, custom made shirasaya.
The blade measures 18cm.