u03bb7 according to this embodiment under visible ambient lighting the see through portion appears transparent and security markings are visible with the same appearance and original color for example black from both sides of the see through portion then when the see through portion is enlightened under predetermined uv wavelengths the appearance of security markings changes and is different on both sides of the see through portion in an alternative embodiment security markings 36 can be applied in negative image in this case when the see through portion is enlightened on its first side that comprises the fluorescent layer shining uv light emits in return a visible colored light through the see through portion coloring the transparent characters of the negative marking read from the second side of the see through portion however in the case where luminescent ink and uv filter are applied on the constitution layers of the see through portion it is important that at least one of the transparent layers 16 19 which covers the luminescent ink does not absorb some uv wavelengths in this particular case it appears therefore to be preferable not to use polycarbonate for such covering transparent layer in a further embodiment not illustrated the security markings are provided in between the developer material and the filtering material the developer material can be for example an uv filter and the filtering material can be for.