Celluloid pinbacks, a type of button, were popular from the 1890s to the 1940s as a cheap way of conveying a political message or advertising anything from food and clothing to movies and tobacco. In 1896 the first patent was granted to Whitehead and Hoag for a button with a textile surface covered with a thin layer of transparent celluloid. Later on the textile was replaced with lithographed paper (cheaper), and ultimately metal without the celluloid.
Advertising pinbacks, sometimes featuring cartoon characters, were often given away as premiums with cigarettes or newspaper subscriptions, or handed out at stores. They were also given as fan club premiums, as part of the membership package. On the political side, pinbacks were given away at campaign rallies.
Some pinbacks are hard to find today because so many were simply worn and thrown away. Collectors also seek to assemble entire pinback series (for example comic character pinbacks) and finding every pinback in a large series can be quite difficult.