For years I have had 4 Indian head cents in my collection. I took them out of their 2x2's for the first time last night. The 1860 is much thicker than the 1887, 1891, and 1899. Whats up with that?
The 1860 is a variety 2 IHC, made of copper (88%) and nickel (12%) and weighs 4.67g. The other three are variety 3, made of 95% copper like pre-1982 lincoln cents, and weigh 3.11g. There was a lot of metal hoarding during the civil war, as I understand it the new IHC were designed to replace merchant tokens that were filling the gap in cent availability (the new cents and the tokens were similar). These changes to the IHC were stipulated in the The Coinage Act of April 22, 1864.