try www.coppercoins.com lots of good pics..or you can buy the book. cherry pickers guide to rare die varieties of us coins.. and of course..lots and lots of reading on this forum
........www.coppercoins.com is quite a site to behold for sure. ........OOPS! i see the site has already been recommended. well then, you can check this one out too. http://www.collectorscorner.org/pocket.html
This hole site is worth your read time and it has most of the knowledge site next to Cointalk will need to look for Lincoln errors. http://www.lincolncentresource.net/forums/index.php