Sadie Adams used a flower with petals for her hallmark. Lena Charlie used an angular ear-of-corn symbol. Jacob Koopee used a stylized kokpelli and Preston Duwyenie uses a symbol he calls "Carried in Beauty" (from an event after his naming ceremony). Marcia Rickey used the flying ant. More people know her as Flying Ant than as Marcia Rickey. There are pieces out there signed by her as "Ant Woman," "Marcia Fritz" and Marcia Rickey.
In the early days of potters signing their pots, many potters couldn't read or write and couldn't sign their name. Many were encouraged to develop a hallmark, an icon, by which customers could better identify their work. That's where all the different symbols came from. Then, as more potters learned to sign their names, the use of hallmarks fell off. These days, it's picking up again, used as an addition to the basic signature. Sometimes it's a clan symbol, sometimes it's a symbol evoked by the meaning of their native name. Sometimes it's just a design that someone likes.
Marcia was a Hopi woman from Walpi. She was active as a potter from about 1950 to about 1990. She made mostly black-and-white-on-red bowls, black-on-white and black-and-red-on-yellow jars, cylinders and lidded cookie jars. Her favorite designs included lots of bird elements, especially feathers.