Euro bank note hologram. Light micrograph (LM) of part of the security hologram on a euro bank note. The hologram is of the euro symbol (blue/green) & the bank note denomination (five, orange), with a background of the word euro in the English and Greek alphabet. The euro is the currency of the euro-zone member states of the European Union, and replaced their national currencies on 1 January 2002. Security holograms are foil patches or strips added to bank notes to discourage counterfeiters. They are known as overt optically variable devices (OVD). When the bank notes are tilted the hologram's symbols change colour. Magnification: x3.4 at 35mm size.