WW2 Japanese Naval sword, Australia

[motto]

The handle should be secured with a dowel that can be pushed or tapped out and then the handle removed to reveal the markings stamped on the tang.
No doubt there will be information somewhere on the interweb that explains what is what or perhaps a reference book is available that your local library can access.
These swords were the souvenir of choice and brought back by the hundred. I recall seeing a photo of a large pile of them at a surrender point, on Borneo I think.
I suspect the chances of it being a traceable family heirloom would be fairly slender but definitely a possibility.

David