Thank you so much for your correspondence!
I have posted a cropped pic of the Tan. The image is poor due to the image size restraints on the forum. It definitely is a square symbol, it was one of the first things I noticed when I first saw the tang!
The katana was given to me by my grandmother who obtained it through her uncle who served during the war. I must get more details as I am sure the history behind it is fascinating.
Thanks again,
Nic