A pharmaceutical dosage form [11, 11g] has reduced susceptibility to counterfeiting, due to the forming directly thereon of a pattern or base layer [10, 10g] of a Moiré pair, wherein a Moiré effect is visually observable by looking through a revealing layer [12, 12g] positioned closely to and superimposed on the base layer [10, 10g]. The pattern formed on the pharmaceutical dosage form [11, 11g] may be formed by embossing, oblation, inkjet printing, or tampon printing. The revealing layer [12, 12g] of the Moiré pair can be part of a blister package containing the pharmaceutical dosage form [11, 11g], so that the Moiré effect is observable while looking at the pharmaceutical dosage form [11, 11g] as it remains within the package.
