Abstract: A stamp (1) is disclosed which has a luminescent coating (9, 11) which over the area of the coating is such that there are a plurality of coated spaced regions interspersed with non-coated regions. The coating may be applied as a grid or cross hatching or other suitable arrangement. The coating is applied over an area which is of sufficient size relative to the thickness and density of the coating to permit the coating to be detected by a postage stamp luminescence detection device. The non-coated regions over which the coating extends being of sufficient area to permit penetration and drying of a stamp cancelling ink. A method of producing such stamp is also disclosed.