Sorry, but IMHO, I think it's a Chinese fake. The blade shape is wrong
for a true tanto (it might (doubtful) be the point of a broken long sword).
The hamon (temperline) looks artificial. The tang patina is bad and the
Kanji don't make any sense - a bad attempt I think at Hiroyuki. The blade
is much too shiney. Overall it look very modernish to me.
I would certainly seek other informed opinions,
but I don't hold out much hope for it. Sorry.
Rich S
The Japanese Sword Index
http://www.geocities.com/alchemyst/nihonto.htm