DOCUMENT OF VALUE AND METHOD FOR DETECTING SOIL LEVEL

摘要

A document of value is provided comprising a soil level test feature for determining whether the document of value is soiled. The soil level test feature comprises: a reference area comprising a first region of the document; and a measurement area comprising a second region of the document. The reflectance of the measurement area is affected differently by the presence of soil or wear to that of the reference area, such that the difference in reflectance between the reference area and the measurement area provides an indicator of the degree of soiling of the document of value.