If you found a sword.
And you lived in Japan.
And the sword had old green papers to Soshu Masamune.
a) Bring the sword to the NBTHK to have a look at seeing as they are right in Tokyo?
b) Put the sword as-is on a second rate internet auction site clogged with junk?
The answer is simple. If you think it’s legitimate you do (a) and if you think it’s fake you do (b) for a few reasons.
There should never, ever be any hesitiation on anyone’s mind when they see something like this. Once something like that goes up, the blade has been explored and kicked around and concluded that it is not worth pursuing. Because doing your homework before you sell it, does not prevent you from selling it as-is. Selling as-is prevents you from doing your homework and finding out if it’s legitimate.
Greed blinds buyers to seller’s self-interested pragmatism. Greed makes them think there is a chance and it’s their lucky day.
There’s only two reasons to buy such an item.
If Masamune is off the target and the judgment was done with good faith, then the other smiths who are nearby the center of the target are all good smiths. Sadamune, Yukimitsu, Go Yoshihiro can all be in play. If the judgment is really far off then you’re going to be dealing with Naoe Shizu and Sue Sa. If the judgment was done in a hostile way, that is, the judge knew he was wrong when he made it, you probably are buying a mumei shinto worth almost nothing.
If you do your homework such a blade can be target for tossing the paper and resubmitting and maybe you get a nice papered Soshu school blade out of it.
Blades like such an item are are fuel for scammers to sell to fools. A deliberately misattributed Masamune with bad old green papers is something that can be bought and then presented to someone without a lot of education and a lot of greed to say, look this thing has Japanese authentication papers, please buy it.
In all cases though, the conclusion is pretty much the same. If you’re looking at a Kotetsu, Shinkai, Masamune, Shodai Tadayoshi, etc., on a Japanese auction site without solid backing, remember those blades are not in the USA.
They have sword dealers. They have teachers. They have Honami. They have the NTHK. They have the NBTHK. It takes a day to get questions answered by top experts. Last time in Japan I saw a guy bring a rusty family Shinto sword into Sokendo, this was not a great sword, but Kurokawa san cleaned it up a bit and explained to this guy what it was and who made it and that it was authentic. You could in fact bring it around to 3-4 good dealers in one day and get those opinions and someone would say try the NBTHK.
So if you have a Kotetsu or Masamune, you’re not just going to go through that process and then turn around and sell it on Yahoo auctions with all of the questionable material still in place. Bad old papers. Faked sayagaki. etc.
Pragmatism is really important, because people sometimes live in a vacuum where they think they are the only one with a clue and so someone might just list a bad looking sword with an old Masamune paper on Yahoo auctions and there’s a chance of legitimacy.
What this is assuming is that people are going to buy a lottery ticket, find out that 6 of the 10 numbers match the powerball jackpot, not check the last 4 numbers, and then put it on ebay for $1. You can make money doing that I’m sure, but you would be making money by selling losing tickets to dreamers.
The situation with eBay in the USA and the rest of the world is different as you have liquidators and sellers who do not want to put the time or effort into something, or don’t recognize it has any value, or have no access to expertise to walk them through the process, or no interest in doing any of that. They just want it gone and quick cash, so even though eBay is still filled with chinese fakes and other junk, people with good eyes find worthwhile items there in the past and still in the present.
This is not to say you can’t find good items on Yahoo Japan, you will, they will be authentic and they will get market value.
You just won’t find the equivalent of the Mona Lisa on there for $500 and nobody bothered to check out already if it had a chance of being legitimate work of Da Vinci before they went to sell it.