I believe the hole positions look odd because the tang has ben shortened.
From what I hear, in the US Robert Benson is one of the best polishers. I cannot recommend him from personal experience, however, just suggest him by reputation. He ID'd my gunto (unsigned tang) to period & school, so I imagine he could tell you something about yours if you want to send it to him for evaluation.
http://www.bushidojapaneseswords.com/
Am I wrong, or is it problematic to send nihon-to back to Japan? I thought they would be confiscated as contraband if not art swords (non-art swords are illegal in Japan), and confiscated as national treasures if they were. Great Catch-22 there.