This is a die trial with "United States of North America" and the date "1875" with no central portion struck in white metal.
It is unclear if this for an obverse or a reverse design or if it is really for a 20 cent piece. It is more likely a design for a medal or token of some sort.
Only 2 are known and both are illustrated. The color example, on a wide planchet, was part of the materials purchassed by the Library Company of Philadelphia from Maxwell Whiteman. It is listed as inventory #14.
Photo courtesy of the Library Company of Philadelphia.
The black and white example is ex Nagy, Kosoff-Bowers and Merena 11/85, Superior 2/91, Early American History Auctions 12/04.
The image is a scan from the Bowers and Merena 11/85 sale.