Hi,
Off topic on:
Tenshin Shoden Katori Shinto Ryu 天真正伝香取神道流 was created by Iisaza Choisai Ieano (1387/1488). This school teach Ken, Kodachi; ryoto (both together), Naginata, Yari, bo (wood stick) and others such fortifications, ninjutsu (espionage) "these two ones are not teached nowadays". this Ryu is the oldest registered in Japan and became Intangible Cultural Asset in 1960. This ryuha was developped for armoured warriors groups not for duel (i would say a battle is nothing else than many duels at the same time and at the same place at least untill the use of firearms).
Off topic off.
Iron is not hard steel. if i'm not wrong, iron tsuba are made in the same metal than the shingane verily less carbonised. Broken tsuba = unusable sword
Do you know what means the term *progress*? Paris ne s'est pas fait en un seul jour