Q. David Bowers (edited and updated by Mike Sherman): The Liberty Head obverse motif was continued during the 1877-1907 span, as was the reverse with IN GOD WE TRUST above the eagle. However, the denomination, formerly expressed as TWENTY D., was changed to read TWENTY DOLLARS, thus creating a new type. Examples were produced in all years at Philadelphia, (although Philadelphia pieces struck from 1881 through 1887 are all rarities, with three of those issues being proof-only) and intermittently at Carson City and San Francisco. New Orleans produced this type only in 1879 (and is rare) and pieces were struck the final two years of the type (1906-07) in Denver. Nearly all issues made after 1892 are considered “common,” particularly the 1904.
Type collectors will find this coin easy to locate in any grade up to, and including MS-65. Above that, the search becomes considerably more difficult. Proofs were made in all years, and while rare and quite costly, are certainly easier to find than proofs of the Type I or Type II varieties.
-- Reprinted with permission from "United States Coins by Design Types - An Action Guide for the Collector and Investor" by Q. David Bowers