specimen stamp
postage stamp or postal stationery indicium sent to postmasters and postal administrations so that they are able to identify valid stamps and to avoid forgeries
en-US/ˈspɛsəmən ˈstæmp/
en-GB/ˈspɛsɪmɪn ˈstæmp/
postage stamp or postal stationery indicium sent to postmasters and postal administrations so that they are able to identify valid stamps and to avoid forgeries