Q. David Bowers (edited and updated by Mike Sherman): In 1866, the reverse of the Liberty Head style was modified by adding the motto IN GOD WE TRUST within the circle of stars above the eagle. The motto was continued from this point forward. This type, minted from 1866 through 1876 is defined by the combination of the IN GOD WE TRUST motto with the denomination below expressed as TWENTY D. In 1877 the denomination was expressed differently, thus isolating the earlier issues as a distinct type. Production was continuous at the Philadelphia and San Francisco mints. Carson City coins were produced beginning in 1870, with the 1870-CC being a great rarity.
Specimens of this second type are available from about Very Fine through MS-63 without a great deal of difficulty. Pieces graded above MS63 however, are few and far between. Proofs exist for all dates, but with an average issue of only 30 pieces per year, are all quite rare.
-- Reprinted with permission from "United States Coins by Design Types - An Action Guide for the Collector and Investor" by Q. David Bowers