I m scientific writer can give you all information about japan coins
20 SEN
worn: $5 US dollars approximate catalog value
average circulated: $12
well preserved: $20
fully uncirculated: $50
coins dated 1873, 1874, 1875, 1891 and 1900 are worth about twice these values
coins dated 1888 are worth about 5 times these values
coins dated 1880 are very rare and are worth $1000 or more