I grabbed that image at random from the American Numismatic Society web site to illustrate the article in last week's E-Sylum. I hadn't seen the medal before, either. It's the Donald Groves Medal, commemorating the Society's move to lower Manahattan in 2004. From the ANS numismatic store page:
This medal commemorates the Society's move from its former home at Audubon Terrace to downtown Manhattan. Designed by Eugene Daub, it was struck in bronze by the Medallic Art Company.