Thanks for the responses guys.
It isn't signed, but it interesting that you think that the nakago may have been cut down. I was thinking the same thing since there are two mekugi-ana, and they are placed rather low relative to what I have seen on other yari. I have heard that the edo period saw many yari cut down and used for home-defense purposes. Also I have seen kago yari used on palanquins during this time, and from what I understand, they had extraordinarily long nakago, but are very rare. So I figured it is likely one of these two kinds of yari, but more likely the former.