I am sure every collector of something has one item they are not entirely sure is genuine, or that is so unique they have never really seen anything like it. Well this piece is both at once.
The box it came in does not concern me at all, as it all looks rather legitimate, what concerns me is seen in the picture. Somehow the center of the foot of this piece is glazed, the place where the artists stamp occurs. So while I can see a place where I think the stamp is, there is no way to really make out the artists stamp on the piece itself.
While the clay looks like something Seigan can easily have done, and the glaze is the Sansai glaze, one of the glazes he is known for. I have recently found out that you can go into certain ceramics stores in Japan and buy premixed glazes that are basically identical to famous glazes. Though a bit of reassurance is inside Japan, Seigan is honestly not famous enough to draw much of this sort of forgery.
So while I am always open to the fact that this piece may not actually be his, I am pretty sure it probably is, but that brings up the fact that this piece is so incredibly unique in other regards.
Notice the square foot. I have never seen Seigan or any other Hagi artist produce a square foot like that.