This is a reverse die trial, struck in lead, of William Barber's eagle on tablet design used on J1530-J1531/P1698-P1699 among others.
Only 2 examples are believed to exist. The illustrated piece is ex Lohr, Batchelder, Cox-Stacks 4/62, Paxman-Bowers and Ruddy 11/74, Werner, ANS. The other, on a square planchet, is ex Raymond 1/43 lot 16, Kosoff - Numismatic Gallery Monthly 7/51.
Photo courtesy of the American Numismatic Society, accession number 1977.202.7.