As often with any large school, there always seem to be many different levels of quality, yet works that are similiar in feeling. I have seen many Nobuie tsuba that have been authenticated of way varying quality. I have been taught that when one sees quite a bit of examples from a large school, most likely there will be dai saku mei works. The Hizen School is a good example, especially during the reign of the 2nd Tadahiro. I believe, no matter what, each piece needs to be judged on its own merits, even when authenticated by any group. For me it is easier to tell a upper grade Nobuie, as I have seen several famous examples, but what seems to amaze me is the amount of works that are available (authenticated ones), especially when compared to those of authenticated Kaneiye. My teacher told me once that Nobuie was a Bushi fashion statement during his time, so they were very popular and thus in great demand. This could be the reason why there are so many examples of varying quality, satisfying all levels of clients. Of course the Dai-Sho set that I saw at the time was top notch , belonging to the Ogasawara Daimyo. My teacher had gotten his information from his teacher Sasano sensei. I was taught that every piece should be judged on its own merits, and by seeing notable great examples, ones eye grows. The theory of Nobuie having students or sons doing work for me is credible just by the shear amount of items that are left that have varying qualty and signatures. All I can say is that one should just learn to recognize the differences between masterpieces and student works and log them in your mind for future references. This will also help you in determining the differences bewtween false signature items and judging unsigned ones. Back to rest as this cold I have is horrible!