Very nice tanto, not a kamikaze dirk. Much earlier than WW II. Handforged
and folded blade. Nice monkey theme fuchi/kashira and menuki. A very
nice same'-nuri saya (sheath covered with polished rayskin). If you can
remove the bamboo peg (they are tapered, so only come out one way),
the entire handle will slide off the tang. If there is any writing (Kanji)
on the tang, please post picture. DO NOT CLEAN THE TANG or Blade.
I suspect this is at least mid Edo period, but that is a guess without
seeing the tang.
Rich
The Japanese Sword Index
http://www.geocities.com/alchemyst/nihonto.htm