My first thought was Choshu over Bushu.
Lead fills in the nakago ana? That is a bit unusual for a Choshu or Bushu.
That threw me a little bit, but I would chalk that up to having been added much later.
Given my hard lean towards flower and tree designs, I remember having seen this design before.
Not common. Memory keeps saying Choshu, though I doubt any one school owned this design.
The inlay has a bit more of the Bushu flair to it.
Ultimately, I'd let the iron tip my opinion between Choshu vs Bushu.