Here are four excellent vintage buttons from the 1930s or early 40s. They are molded of white plastic with self shanks on the backs. They measure just shy of 1.5 inches in diameter. The condition is as perfect as vintage buttons can be.
These may be Bakelite plastic but they do not pass the hot water test and that is the only test I know that doesn't damage the item. They feel like old radio or telephone plastic.