In 1864, the Philadelphia Mint produced two versions of the Two Cent piece, both relating to the size of the letters in the motto IN GOD WE TRUST. The Large Motto replaced the Small Motto and became the model for the remaining years of the Two Cent type. The Large Motto variety is the more common of the two. Cherry-pickers should keep a lookout for the following scarce and interesting varieties:
1864 Large Motto, Doubled Die Obverse
1864 Large Motto, Triple Punched Date
1864 Large Motto, Reverse clashed with the obverse die of an Indian Head Cent!
Sources and/or recommended reading:
"Getting Your Two Cents Worth" by Kevin Flynn
"Two Cent Piece - An 1864 Attribution Guide" by Frank Leone
"Cherrypickers' Guide, Fifth Edition, Volume I" by Bill Fivaz and J.T. Stanton