Piggy bank (sometimes penny bank or money box) is the traditional name of a coin accumulation and storage receptacle; it is most often, but not exclusively, used by children. The piggy bank is known to collectors as a still bank as opposed to the mechanical banks popular in the early 20th century. These items are also often used by corporations for promotional purposes. Their shape is most often that of a little pig.Piggy banks are typically made of ceramic or porcelain, and serve as a pedagogical device to teach the rudiments of thrift and savings to children; money can be easily inserted, but in the traditional type of bank the pig must be broken open for it to be retrieved. Most modern piggy banks, however, have a rubber plug located on the underside; others are made of vinyl and have a removable nose for easy coin access. Some piggy banks incorporate electronic systems which calculate the amount of money deposited.