Thank you for sending my mind to reality, I had forgotten the Meiji reform of the calendar in which Western style calendar became the official one when the Japanese one was maintained for" spiritual" reasons but was made to comply.
In disorder:
. There is no stamp nor credible marks which would lead to believe one as been removed.
. Sori is 17/18 mm, Tori sori.
. photos attached, I should have sand blasted glass to diffuse the light and work on my lighting.
. Temper line crisper than my photos taken with macro, hand held camera.
. Yes the tang has been tempered with, initially I thought it was a very badly finished one and after your comments, I rubbed it wit a soft cotton cloth and got some kind of graphite grease ( I used that type of grease in the 1980's).
Warm regards
Michel
