1. An authenticatable product comprising a non-opaque latent image layer of anisotropic polymer material having background optical properties with a given preferred direction of anisotropy and a given proportion of crystallinity, said latent image layer being treated so as to include: (a) a first localized modification in said latent image layer, said first localized modification being associated with a first latent image and modified in at least one of said given preferred direction of anisotropy and said given proportion of crystallinity; and (b) a second localized modification in said latent image layer, said second localized modification being associated with a second latent image and modified in at least one of said given preferred direction of anisotropy and said given proportion of crystallinity such that, when viewed directly, said first latent image and said second latent image are indistinguishable from the remainder of said latent image layer and, under polarized visualization, a maximum contrast between said first latent image and the remainder of said latent image layer is actualized at a different orientation of polarized visualization than a maximum contrast between said second latent image and the remainder of said latent image layer.