3/4” square, NBS medium.
Good condition, original plastic shank. I think this guy looks like a Martian, maybe a Mayan, who knows? Samoth Ceramics were made in Oakland, California in the mid 20th century. Despite exhaustive research, that is the extent of what is known about this company. Their designs are colorful and whimsical and are catching the attention of button collectors across the United States.