This is a reverse die trial of the central portion of the seated liberty design. Pollock lists this under 1842 as the eagle is of the large letters design used from 1842 to 1891. It was likely struck in the mid to late 1860s as the first example listed below was struck in aluminum.
Exammples are known in several metals as follows:
Aluminum P3085 ex Stacks 6/87, Stacks 5/01.
Copper P3090 ex Heritage 10/91. This may be the same as the C.E. Meyer pedigree listed by Pollock.
A second example in copper and aluminum was part of lot 2368 in Ira & Larry Goldberg Coins & Collectibles 6/04 sale.
Note: The example in Zinc? with a tab on the edge P3088 listed as lot 461 of Stacks 6/88 Sprinkle sale is a complete die trial including the legends "United States of America" and "Half Dol". It is misdescribed in Pollock.
Note: The genuineness of these pieces has been questioned so they were not assigned numbers in the new Judd book pending further analysis.
Photo courtesy of Stacks.