To me it looks like something that might have been offered for sale to a GI during the post war American occupation of Japan .
Possibly a re-mounted Japanese war prize :
http://tinyurl.com/c5m3x
Perhaps even the ultimate in irony right down to the blued blade ; 1917 model US Navy cutlass :
http://tinyurl.com/ajfeg
I wonder if the new owner will post pics of it here ?