Retsuden Stamps (スタンプ烈伝) are Japanese stamps made by the Ensky company. "Retsuden," when searching on a site such as Yahoo!Japan, can refer to many things in a series, but when collectors refer to Retsuden, they mean this particular set of stamps. The series has been around since Advanced Generation. Each Retsuden features a single Pokemon and has an unscrewable base which reveals the stamp. Though Retsuden have only been made since Gen III, Pokemon from every generation are featured, some more than once.