Princess Europa will appear on the €5 note in May 2013, with other notes introduced in ascending order in the next few years. Princess Europa's face will be shown as a watermark and as a hologram. The new notes will also carry an emerald-coloured number. The first series of banknotes will circulate alongside the old ones. But the old notes, first introduced 10 years ago, will eventually cease to be legal tender. The old notes will retain their face value and will be exchangeable at any national central bank in the eurozone even when they are no longer valid in shops. Meanwhile, counterfeiting euro notes has kept international law enforcement authorities busy. This being the reason for more secure euro notes.