I feel that in times of war, or a big order from china, many swords were not signed.
If you have a town full of smiths, cranking out dozens of swords every week (or more), I'm sure most of those swords went unsigned.
That is likely, one of the reasons why we see so many unsigned swords. Most sword makers were businessmen. If a sword was a bit "off", as long as it had no fatal flaws, it would likely be assigned to the "bin". To be sold as is, to whomever. Forever unsigned.
They still worked for what they were intended.
Once in a while you see that wonderful, ubu, unsigned sword and it makes you go hummmmmmmmm??
It is likely, that even some of these "bundle" swords were very pretty, even flawless.
Just another reason why.