Hi David,
thank you very much for the hint! Actually I did not want to call it either Bishu or Owari and therefore I called it both !
Because: on the one hand, there are Tsuba traditionally classified as Owari tsuba. But - only judging from pictures - I cannot detect the classical Owari tsuba criteria, e.g. tekkotsu, etc.
On the other hand, the signature on the reference tsuba clearly indicates that this tsuba was made in Owari 尾張 (or Bishu 尾州). Therefore I could have either called it a Bishu tsuba (which I have never heard of, especially in terms of Yagyu producing schools) or a Bishu Owari tsuba (what I did). Of course, that might sound a little bit overdone...
Best wishes,
Chris