1. A printed document including a machine-readable signal comprising: a first set of print structures conveyed with first ink; and a second set of print structures convey with optical variable ink, the second set of print structures comprises breaks in lines, with the second set of print structures conveying a machine-readable plural-bit auxiliary signal, wherein the second set of print structure are provided to cooperate with the first set of print structures so that at a first observation angle the first set of print structures and the second set of print structures appear to provide a first visibly perceptible feature; and wherein at a second observation angle the second set of print structures appear less observable so that the first set of print structures and the second set of print structures provide a second visibly perceptible feature.
1. A printed document including a machine-readable signal comprising: a first set of print structures conveyed with first ink; and a second set of print structures convey with optical variable ink, the second set of print structures comprises breaks in lines, with the second set of print structures conveying a machine-readable plural-bit auxiliary signal, wherein the second set of print structure are provided to cooperate with the first set of print structures so that at a first observation angle the first set of print structures and the second set of print structures appear to provide a first visibly perceptible feature; and wherein at a second observation angle the second set of print structures appear less observable so that the first set of print structures and the second set of print structures provide a second visibly perceptible feature. 3. The printed document of claim 1 wherein the breaks are due to the appearance of the optical variable ink at the second observation angle.