Patent US 4,582,986

For the characteristic marking of a data-carrier, for example a cheque- or personal authorization card, its specific physical properties, e.g. optical properties, are scanned in a first data-carrier region, converted into characterizing data and recorded as an authenticity record on the data-carrier itself or in a processing station. For subsequent authentication or authenticity identification of the data-carrier, its physical properties are scanned in a region thereof which comprises the region scanned for the characteristic marking process but is larger than this. The two sets of data derived from the said two scanned data-carrier regions are then mutually compared to trace points of coincidence by application of correlation-and signature-analysis-methods. For identification, or authenticity verification of the data-carrier the latter need no longer be lined up relative to the scanning device which scans its physical properties in precisely the same position as it was during the characteristic marking process.