A rather new addition to the 'RedBook' are 1998, 1999, and 2000 'WIDE AM' Lincoln cents (all from Philadelphia mint - no mintmark).  Also referred to as 'Type 2' reverses, these varieties were made with reverse dies intended for PROOF cents.  They are easily identified by a space between the A and M of AMERICA.  The space is wide enough so it can even be seen without magnification!  On normal coins of these dates, the A and M are nearly touching.  All 3 can be found in pocket change and bring a substantial premium over face value.  $10 - $40 for the 1998 and 2000, and $100 - $300 for the 1999

These coins are still in circulation and with enough searching, you WILL find one.