<Tr> <Td> 23rd </Td> <Td> </Td> <Td> </Td> <Td> Silver plate </Td> </Tr> <Tr> <Td> 24th </Td> <Td> Opal </Td> <Td> </Td> <Td> Musical instruments </Td> </Tr> <Tr> <Td> 25th </Td> <Td> Silver </Td> <Td> Silver </Td> <Td> Silver </Td> </Tr> <Tr> <Td> 30th </Td> <Td> Pearl </Td> <Td> Pearl </Td> <Td> Diamond </Td> </Tr>

How many years does a silver anniversary celebration
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