Thanks for the complement, Fernando, but it was just a case of having the right books! Thanks as well, Gene, for hoping I'm right!
This is a case where provenance will greatly help the piece. If it is from a colonial dig site, perhaps there is paperwork to show this? Old photos from the dig site or an original documentation log of the piece? This is one of those situations where it would greatly increase the identity of the object, perhaps to the point where one could even identify the tribe that might have used it. Iron axes followed the settlers over and were trade items made by the French and English fur traders. Interestingly, the Spanish who superseded them were not into the trade thing. Likewise, the Dutch didn't wrangle with the Native Americans much. In any case, I bring this up because most of the Native American tomahawks were not made by them, but by the European traders themselves. Thus, you see them with rounded butts, single-bearded/double-bearded, thickened spikes, etc-i.e. A lot of artistic licence.
Chris, I hope your friend can find some provenance, as this would be a very valuable piece...