You got you decimal point in the wrong place for the half dimes. The correct answers should be; .145 Grams Half Dime1794-1837 .134 Grams Half Dime 1837-1853 .124 Grams Half Dime 1853-1873 Also, how about the One Cent 1982- present (with exceptions); .020 One Cent 1982- present BTW, that makes the zincon's copper content the second lowest of all American coins.