| 摘要 |
A document is provided having thereon a legible code to distinguish the document from other similar documents, the code comprising an arrangement of alphanumeric characters. Where the document is a banknote, the code may be the serial number which is unique to that banknote, and which is one of a series of such serial numbers carried on individual members of a set of such documents, and having sequential numerical values. To enhance the security value of the serial number portion of the document and to inhibit successful forgery thereof, the alphanumeric characters are provided in reverse, or negative form. The security value derives from the complexity and cost of the apparatus necessary to print a series of successive serial numbers in reverse, rather than positive form. The code may correspond to a code provided elsewhere on the document in positive form. Another reverse code on a different background may be provided elsewhere on the document. |
