A method for printing an original image which is protected against copying or alteration, such as a postal indicium, and for determining if that image has been altered. The image includes a copy detection feature and coded information linked to the copy detection feature. Altered images are detected by testing to determine if the link between the copy detection feature and the coded information in fact exists. The copy detection feature and the coded information can be linked by: 1) scanning the image to recover the coded information and the copy detection feature; 2) test the coded information and copy detection feature, and 3) accept the printed image as unaltered if the test indicates that the nominal link exists in fact.