I've been sorting out my late Dad's stuff. Tucked away in the attic was a Katana, not the bike, the sword. It's a type 95 NCO Katana from the Kokura Arsenal, Suya sword shop. Apparently they were mass produced and are not particularly rare or valuable.
Looks like this one:
https://www.gunstar.co.uk/suya-sword.../Blades/991380
only in worse condition.