<Tr> <Th> Notable stones </Th> <Td> Cullinan II, St Edward's Sapphire, Black Prince's Ruby, Stuart Sapphire </Td> </Tr> <P> The Imperial State Crown is one of the Crown Jewels of the United Kingdom and symbolises the sovereignty of the monarch . </P> <P> It has existed in various forms since the 15th century . The current version was made in 1937 and is worn by the monarch after a coronation (St Edward's Crown having been used to crown the monarch) and used at the annual State Opening of Parliament . </P> <P> The crown is adorned with 2,901 precious stones, including the Cullinan II diamond, St Edward's Sapphire, the Stuart Sapphire, and the Black Prince's Ruby . </P>

When was the last time the queen wore the crown
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