Variety equivalents:
Judd 1404 = Pollock 1547 =
Adams-Woodin 1447

Designer:
Obverse: William Barber
Reverse: William Barber

Rarity: Very Rare

Metal content: Copper

Edge: Plain

Patterns for a Twenty Cents coin were first proposed in 1874, in response to a request from Western states, whose populace held non-silver coins in disdain yet complained that they did not have enough coins to make small change!  The new denomination was authorized by the Act of March 3, 1875 and production began on May 19, 1875.

All the pattern designs of 1875 were created by William Barber, who adopted a nautical theme for the year.  His "Sailor Head" design (Judd 1392-1395) lost out to the Seated Liberty design, which matched stylistically the coins already being produced by the Mint.

Images courtesy of Ira & Larry Goldberg Coins & Collectibles

Significant examples:
Ira & Larry Goldberg Coins & Collectibles, Inc.'s "The Benson Collection" Sale - Part 1, February 18-20, 2001

Notes:
Pollock recorded six weights ranging from 55.2-61.9 grains, two diameters of .86 inches, and he noted that all the examples seen by him had a 180 degree die alignment.

Judd called the obverse "Liberty at the Seashore."

The reverse of this Pattern was also used on 1874 Pattern Twenty Cents (Judd 1357 and 1358).

Sources and/or recommended reading:
"United States Pattern, Experimental And Trial Pieces" by J. Hewitt Judd, M.D.

"United States Patterns And Related Issues" by Andrew W. Pollock III