April 18, 2012 (CHICAGO) --There's a rare penny that's expected to sell for more than $1 million at an auction in the suburbs. It's one of the first coins ever struck at the US Mint; an experimental copper cent. The penny has a small silver plug in its center and 14 are known to exist. There will be a public auction of the rarity tomorrow night in Schaumburg. There is already an online big of $1.1 million.