Abstract: A composition for rendering materials fluorescent substantially without visible trace comprises an organic fluorescent compound dissolved in a solvent characterized by a boiling point or distillation range at atmospheric pressure of between about 12.degree.-35.degree. C. The preferred composition comprises fluorescent azoles, such as 2-(o-Hydroxyphenyl)benzoxazole, 2-(o-Hydroxyphenyl)benoxazole, and derivatives thereof dissolved in volatile halocarbon solvents, such as Fluorotrichlormethane, 1,1-Dichloro-1-Fluoroethane, and 2,2-Dichloro-1,1,1-Trifluoroethane. The resultant product is particularly suited for marking currency, papers, fabrics, and other porous webs and surfaces. Treated surfaces appear normal in white light, are highly fluorescent under UV light and feature excellent transfer of the fluorescent compound to fingertips and other surfaces in direct or glancing contact.

Abstract: A firearm having marking elements as an integral part of its bore surface which are arrayed according to a code indicating the identification number of the firearm so that any bullets fired therefrom will bear markings corresponding to the marking element array which markings will indicate the identification number of the firearm. The marking elements being an integral part of the firearm cannot be removed without damaging or disabling the firearm. A wide variety of marking element arrays are possible so that a large number of identification numbers may be encoded.