An identification method, for determining whether a sample of an unknown composition is a sample of a known composition to which a known amount of a SERS-active taggant compound has been added, includes the steps of: obtaining a sample of the unknown composition; adding to the composition a plurality of SERS particles to form a mixture, each SERS particle including:—a core including a nanoparticle having a plasmonic surface,—a SERS-active internal standard compound adjacent the plasmonic surface and,—a shell, the shell encapsulating the core and the SERS-active internal standard compound; obtaining a SERS spectrum from the mixture; and comparing the SERS response ratio SATC:SAISC from the SERS spectral response of the SERS-active taggant compound and the SERS spectral response of the SERS-active internal standard compound in the unknown composition with the SERS response ratio SATC:SAISC from the known composition.