I second Steve's advice. Look up the silver book or the golden book by Sasano.
Tell you what, Evan, it is just a hunch. If Sasano has put one into tye Owari basket and another one into the Shoami grab bag, I won't say I know better. So treat this just as a feeling, intuition that cannot be confirmed, nor concusively denied.
And, BTW, an eventual NBTHK origami to Owari or Shoami will be... just an opinion.
Get the Sasano books, read about Kanayama, for that matter. An interesting study in speculation. Attributions of old tsuba should always be treated with a grain of salt - they are in most cases just the result of an understandable desire to categorise, but, frankly, they are meaningless in cases where there are no documented lineages of tsubako.
In this sense, my opinion does not matter at all. Try to pinpoint the aetshetics, without getting bogged down in all those seppa-dai and rim shapes. In the case of this tsuba it will be an exercise in futility. Enjoy it, understand the iron, look at the workmanship, but don't insist on "boxes".
Just my two cents...