1. A secure document comprising: A synthetic core, the synthetic core comprising a polyolefin polymer and particles distributed in the polymer, the particles each comprising layers of material, the particles having at least one visible color such that the dispersed particles provide a visibly verifiable authentication attribute for the core material; the particles having a non-visible forensic material; wherein the forensic material has a distribution within the synthetic core that is readable by scanning the secure document with an illumination source; and, wherein a representation of the distribution is encoded in a machine readable data carrier within the secure document.