1. A pressure-sensitive image-transfer sheet, comprising: an inert base layer of flexible material; and a transfer layer, for transferring to a front surface of a document, coated upon the base layer, the transfer layer comprising: a ferromagnetic material for producing magnetic indicia for detection by a magnetic sensing system when the layer is transferred to the front surface of the document; an oil soluble organic dye for producing visible verification, on a reverse surface of the document, of the authenticity of the magnetic indicia after the layer has been transferred to the front surface of the document; a substantially nonvolatile, substantially nondrying oil for dissolving the organic dye; and a binder for holding the magnetic pigment, the organic dye and the oil in the layer and for adhering to the front surface of the document when the layer is transferred to the document upon application of pressure to the transfer sheet, and wherein neither said organic dye nor said nondrying oil are microencapsulated.