Since the Meiji era the family has done the whole production process.
The secrets are passed down from parent to one child of the family.
This is a great book for identifying Fukagawa, Koransha and Seiji Kaisha during the Meiji period and into the first part of Taisho.
It is in Japanese but there are many marks and some have western dates associated with them.
A stoneware pillow in the Sir Percival David Collection bears an incised poem by the emperor Ch'ien Lung calling it Chai ware, but it is virtually indistinguishable from Chn.
The marks were hand painted back then so there is a bit more variety in the marks.Hasami and Mikawachi are actually in Nagasaki Prefecture.