Quote:Proof verses Business Strike
There are two distinct types of Lincoln cents minted, the Proof type minted for collectors and the Business strike minted for general circulation.
Proof coins are minted with highly polished dies and struck multiple times to give a highly detailed and shiny, mirror like finish to the coin's surface. They will also have sharper rims than business strikes.
http://www.lincolncentsonline.com/history.html Quote:There were
no mint marks on Proof cents minted from 1909 - 1964, after that, they have an S mint mark from San Francisco.