I have read this statement on Aoi-Art website :   First the link : http://www.aoi-art.com/sword/katana/07557.html   Then statement :     Is this statement relevant or not?   When did start, thrive Kazu-uchi mono production during the warring states period? Tai-Ei?   Can we say that a Bishu Osafune mei with a nengo is a Kazu-uchi mono? http://www.aoi-art.com/sword/katana/06222.html Can we say that a Bishu Osafune mei + original hi is a Kazu-uchi mono? Where do stand niji mei blades