What this coin looks like (obverse, reverse, mint mark location, special features, etc.): There were a few major varieties of the 1858 Flying Eagle Cent (Penny). One variety had small letters while the other had larger letters on the obverse of the coin regarding the words "UNITED STATES OF AMERICA". The best way to indentify the variety is to notice that the "small letters" variety has a large space between the first two letters "A" and "M" in the word America. The large letters variety has almost no space and the two letters are almost touching. This is depicted in the example image above of the 1858 small letters vs large letters flying eagle cent.
In addition: There is also a rare 1858/7 overdate error coin where the 1858 date was stamped on top of a 1857 date.