Back to topic... the Naginata that Marius posted is good for comparing to the other naginata in discussion. Funny enough they kinda look similar. The one Marius posted looks mid-late Edo (hard to tell for sure because of the lit up patina on Nakago).. Pretty short and beefy. Sugata is almost a balance in length in Nagasa X Nakago. The original posted naginata had a longer Nagasa and shorter nakago ..slightly slimmer Sugata.. Id think the OP naginata is older (earlier Edo) than Marius's and actually slightly suriage. All speculation and uneducated without seeing OP nakago. Jean, I agree, when comparing a Koto blade with "a good example of dark steel" vs a shinto or newer, it is obvious that the steel of old swords is considerably darker. Thinner and lighter blades too. Shinto steel is "generally" lighter in colour as opposed to Koto. Jean and Jacques.. exceptions to all rules right? Occasionally there is shinto blades with "darker" steel and koto with "brighter" steel. Jean is correct about the transition of steel quality from Koto to shinto and I'm sure Jacques is right too about yasutsugu .. didn't he and other shinto smiths experiment by sourcing old steel to use when making their swords? Just my Thoughts .. oh and I agree with you,Luis.. you start to develop a "sixth sword sense" haha.