Correct.. Weight, thickness. Also the color https://www.coinstudy.com/1864-indian-head-penny-value.html
Here is an 1864 copper-nickel. These coins are white, like the modern nickel when they are pristine. They become greyish in circulation. The corroded ones are mostly black. This one is Choice Mint State, but it's toned. Here is a mostly Red, Mint State 1864 Bronze cents. I think that this coin is a tad underrated.
That kinda scares me. I have all of the IHCs except for 1877. Now I have to take them out and really look at them. I let you know what I find or don't find. Thank you.
Thank you everybody, I held the copper and bronze together and it was very obvious the copper was twice as thick as the bronze. Case closed
http://www.indiancentvarieties.com/index.html I find this site for IHC's has a lot to offer. Not to mention I have a few plate coins on that site.