This is obviously a katana ( http://imgur.com/a/Ua97X ) but what kind and who would of held it. This was given to us from my grandfather who served in the pacific during WWII. I hope this is the appropriate subreddit for something like this.
To get any real help we'd need to see the end of the blade closest to the handle. Are there any markings their at all? What is the total length of the blade?
r/swords and r/knives would probably be better able to help.