This is the completed reverse die trial of JA1857-8/P3152, in copper, of a Heraldic eagle design by Anthony C. Paquet. It was never combined with any obverse.
For additional information on this, please refer to the article on the 1861 Paquet dollars in the ANA Centennial Anthology.
It is unique and is ex Lefferts (S.H. & H. Chapman 7/1881 lot 723), Britton (G. Cogan 1/1883 lot 405), Garrett-JHU, Bowers and Ruddy 3/80 (Garrett II), Heritage 1/19 FUN - PCGS64RB.
Photo is a scan from the Garrett II sale.