I have some really problems to judge a blade in age.
Hamfish shows today an ebay offer of a Gunto with "old" blade. The sword is sold, but i tried today to find out if this blade was a gendaito, a shinshinto or older blade. I didn't know.
The sword had some flaws, that is not typical for wartime gendaito. The shape is typical showa, in my eyes. But the nakago has a deep patina.
What is your suggestion about the period of this blade. If you could explain why?
http://vi.vipr.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=222713734302&t=1510300807000&tid=10&category=66841&seller=koushuya&excSoj=1&excTrk=1&lsite=0&ittenable=false&domain=ebay.com&descgauge=1&cspheader=1&oneClk=1&secureDesc=0
I hope to learn something.