This is a ko-wakizashi (small wakizashi) or o-tanto (large tanto) - your choice. Normally tanto are under 12 inches and waks are 12-24 inches but many are borderline (like yours). It is mumei (unsigned) and has been remounted at least once (has two mekugi-ana) tang holes. The fuchi/kashira (collar and end cap) are in a kabuto motif (Japanese helmet). Condition is not good, so can't tell anything about the hada (steel grain) or hamon (temperline). It would take a good Japanese sword polisher to restore the blade. For the time being I'd suggest just apply a very thin coat of oil to be the blade (not enough to make droplets - don't want oil running into the saya (scabbard). Wish I could tell you more, but that's all I can see in it's current state.
Japanese Sword Guide