"In philately, indicia are markings on a mail piece (as opposed to an adhesive stamp) showing that postage has been prepaid by the sender. Indicia is the plural of the Latin word indicium, meaning distinguishing marks, signs or identifying marks. The term imprinted stamp is used more or less interchangeably, but some indicia are not imprinted stamps. One example is the handstamp, which can be seen in a photo on this page." - (en.wikipedia.org 29.02.2020)
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