In 1803, the Papal States started using a white merchant flag with the Papal coat of arms in the centre. This flag was made official on 7 June 1815. On 17 September 1825, it was replaced with a yellow and white flag which took its colours from the materials of the key (yellow for gold, white for silver). These colors were probably taken from the 1808 flag of the Palatine guard. This was the first bicolour used by the Papal States and the ancestor of the modern flag of Vatican City. The merchant flag also served as a state flag on land.