The medal's obverse bears bust of Washington Allston, facing right. Around left and right, WASHINGTON - ALLSTON; signed at bottom, P. P. DUGGAN DEL. C. C. WRIGHT SC.
The reverse bears standing Columbia with American shield, crowning two artists, one holding sculptor's mallet, the other painter's pallet and brushes, on step below. Around top, AMERICAN - ART-UNION; signed and dated on steps, P.P. DUGGAN DEL. / 1847 - C.C. WRIGHT SC.
Washington Allston (1779-1843) was a famous American painter and poet who was born in Waccamaw River, South Carolina. After traveling a lot, he spent most of his later life in Cambridge, Massachusetts. He is buried in Harvard Square. A western suburb of Boston, Allston, is named after him.
This was the first medal in the American Art-Union medal series.
The circular medal measures 64.2mm in diameter and was struck in bronze at the U.S. Mint. No mintage is reported.
Many thanks to eBayer Pat who granted me permission to use the images of the silver variant and to Tom Rogahn who pointed them out to me.
References: AAU 1, Storer 1860, Marqusee 409