The present disclosure provides apparatus for analyzing emerging security or authentication feature for physical objects (e.g., identification documents, product packaging, banknotes, etc.). One claim recites an apparatus comprising: a light source for illuminating a physical object with first non-visible light, the physical object comprising a first code provided with a first ink or dye and a second code provided with a second ink or dye, the second ink or dye comprising an emission decay time that is relatively longer than an emission decay time of the first ink or dye, the first code and the second code collectively conveying a first feature when illuminated with the first non-visible light, with the second code individually conveying a second feature after emissions attributable to the first code fall to a first level; and an electronic reader programmed for reading at least the second feature after emissions attributable to the first ink or dye fall to the first level and before emissions attributable to the second ink or dye fall to a second level. Other claims and combinations are provided as well.