Swirl pottery collection

I am drawn to swirl pottery.
These are a few small pieces I have.
The tallest vase 5 1/2" on the left is stamped on the bottom Skag Ozark USA pottery. Not a lot of information on this company that I have found. It is made of onyx cave clay. Not the same thing as Ozark roadside tourist pottery.
The center vase is marked with a faint number, but I believe it is a Nemadji pottery 3 1/4" tall. Beautiful sunset colors.
The last one miniature sundried clay basket is 3 1/2 tall and looks like pieces of Gay Head pottery, Aquinnah, Massachusetts on Martha's vineyard. I would like to verify this, but so far haven't found anyone to contact. Any information would be helpful.