Jacques,
You should stop reacting at my posts, it is becoming an obsession (a boring one) which leads you to quote me and add a stupid example as proof.
You should read late Jean d’Ormesson « dislike is bad for health »
As everyone knows, Yasutsugu is late Shinto/Shinshinto ????
The Yasutsugu (first generation) began forging still in Koto times. Don’t try to biaise as usual the discussion.
Here is an article which settles things concerning the steel in Shinto and Shinshinto times:
http://jssh.org/shinto.html#/3
So, goodbye the theory of dark steel in late Shinto, Shinshinto.
To come back to Yasutsugu, we can’t say that it is a kantei point of Yasutsugu (perhaps in its youth), for to be a kantei point, it must be a constant in the smith forging which is not the case, taking into account the number of blades made of namban tetsu. All can be said is that some of his blades have the dark steel colour of northern provinces.