What materials are in a tambourine?

Proper tambourines as used in music have a circular wooden frame, in which slots are carved that contain small concussive opposing rings shaped like miniature cymbals, which are known as the 'bells' and can be made either of brass or a lower metal alloy. The drum-section of a tambourine is usually made of animal hide, usually calf-skin. However, toy tambourines for children often use plastic to make the frame and the drum (although some proper tambourines can have high-quality artificial frames as well).