sentences:  Pre-2006 stamps denominated only in lira remained valid for use until 31 January 2008, and they could be exchanged for euro-denominated stamps until March 2008, after which they were invalidated.The dual currency stamps issued since December 2006 remain valid for use today along with euro-denominated stamps.A definitive set which commemorated events in Malta's history was issued in 2009, and two further stamps were added to the set in 2012 after postal rates had increased.