The Hopi potters didn't really start signing thier pieces until after Fannie Nampeyo began signing for her mother, around 1925. Even then, many potters didn't sign their works for another 20 to 30 years. It seems only the Nampeyo family saw the value in that.
Anyway, since Nampeyo first started to see success, more and more Hopis and Hopi-Tewas saw the value in creating pottery as art work for the tourist trade. It was still a while before most of them began to sign their works. So we have a lot of relatively modern Hopi pottery we can't attribute to any one potter.