Roger, it is a difficult one, I think. Earlier schools are often related with (relative exact) time periods, while later ones are sometimes difficult to differentiate from each other. Design elements had spread around in the country and in the TSUBASHI workshops and were copied which makes an exact judgement much more difficult. In your TSUBA I see features like the SHINSHU droplets representing water spray on the waves. The way this is carried out reminds me a bit of ONIN TSUBA - not saying this could be related to that style but perhaps the artist had something like that in mind. The design - waves and a water wheel - is a common one and was used by many schools. The heavy corrosion does not make it easier to find an assessment, but my gut feeling and the fact that some of the brass inlays have fallen out leads me to believe that it is not an early TSUBA, so my guess is somewhere about 1750 or later This opinion is a bit bold, so I am happy to be corrected.by our experts.