a duplicate of a typeform (type and cuts) used in letterpress printing, consisting of a one-piece plate 2–25.1 mm thick. Stereotypes first appeared in the 18th century and are now widely used to print large numbers of copies. Stereotypes are classified according to the method used to produce them as cast (made of type metal), electrotyped, and molded. They can be made entirely of metal (type metal alone or type metal with a layer of a more durable metal deposited on the printing side) or of polymer (plastics or rubber), or they can be made of a combination of a metal and polymer (metal on the printing side and polymer on the reverse side). The shape of rigid stereotypes—those made of metal or of metal and a polymer—depends on the type of printing press used. Flat stereotypes are used with platen and cylinder presses. Curved stereotypes are used with rotary presses.