euro on 1 January 2008. Stamps issued shortly before and after the changeover (between 22 December 2006 and 28 June 2008) were denominated in both the Maltese lira and euro currencies in accordance with guidelines issued by the National Euro Changeover Committee. 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 demonetized. The dual currency stamps issued since December 2006 remain valid for use today along with euro-denominated stamps. Prior to adopting the euro, Malta had demonetized stamps a number of times, for example all pre-1998 stamps were invalidated in December 2004. Netherlands Stamps of the Netherlands denominated in guilders were demonetized on 1 November 2013. It is not possible to exchange guilder stamps for ones denominated in euros. Portugal Portuguese stamps denominated in escudos were demonetized in 2002. All stamps issued since 15 March 1999 are valid for postage. Spain Spanish stamps denominated in pesetas were demonetized in 2002. All stamps issued since 8 January 2001 are valid for postage. Vatican City Stamps of the Vatican City denominated in lire are no longer valid for postage. Australia The six self-governing Australian colonies that formed the Commonwealth of Australia on 1 January 1901 operated their own postal service and issued their own stamps. Under section 51(v) of the Commonwealth of Australia Constitution 1900, “postal, telegraphic, telephonic, and other like services” became a Commonwealth responsibility. The Commonwealth's Postmaster-General's Department became effective on 1 March 1901 (this agency would be disaggregated on 1 July 1975 in part into the Australian Postal Commission trading as Australia Post). All then-current colony stamps which continued on sale became de facto Commonwealth stamps. Some of these stamps continued to be used for some time following the introduction in 1913 of the Commonwealth's uniform postage stamp series. These stamps continued to be valid for postage until 1968. Pre-decimal Commonwealth stamps were valid till the 14th of February 1968, exactly two years after decimalisation. Hong Kong In Hong Kong postage stamps have been demonetized only once, which happened because of the 1997 handover. Postage stamps from before 1997 bear the portrait of the king or queen of the United Kingdom (who at the time of handover was Queen Elizabeth II). Although there was already a series of politically neutral stamps issued (which did not bear the portrait of