Gral question

[Luis22]

Hello Guys,
I was wondering if someone could answer my question. I know that the Nakago is the main source to identify the age of a blade or who made it.I have seen blades in some nihonto websites that claim that the sword is several centuries old and there is almost no rust on them?? What would be the condition of a nakago that's several hundred years old?? I know that preservation has a big role on the condition but I would expect to see some pattina on the nakago fopr such an old item...
See example here ..http://www.nihonto.ca/ko-hoki/index.html
thanks,

[Beater]

As a rule of thumb, the rust darkens, the older the sword. Black, smooth rust is likely Koto. Brown rust Shinto. As you correctly note, how well a sword is kept may delay this to some extent. Also, when a very old blade is o-suriage and has had the original tang cut off, the colour will often be less dark because the tang was once part of the polished blade.
The tang is only one clue though. The blade steel colour, blade shape, worn ha-machi, feint yasuri-mei, tang tip shape and many other features will all provide indications.