Hi,
I say nothing.... they say. you must write to them and say "sorry but you are wrong".
An other exemple.
http://www.k3.dion.ne.jp/~j-gunto/gunto_147.htm
Read also the connoisseur's book of Japanese swords (Page 33) and Comments on the Construction of Japanese Swords by Harvey Stearn, BUSHIDO: An International Journal of Japanese Arms, Vol 2, No. 3, January 1981.
You can believe what you want, it's not my problem.