Yes, there is an actual medal.
It comes in a beautifully crafted wooden box lined with deep blue velvet. The medal itself nestles inside a perfect indent of a circle made to fit the medal exactly. A matching deep blue grosgrain ribbon makes it possible to easily remove the medal from its circular housing. One side of the medal shows a man (presumably John Newbery himself) presenting a book to two children. The other side is an open book on which is inscribed:
FOR THE MOST DISTINGUISHED CONTRIBUTION TO AMERICAN LITERATURE FOR CHILDREN
KAREN HESSE 1998
On the same side, written around the perimeter of the medal:
JOHN NEWBERY MEDAL AWARDED ANNUALLY BY THE CHILDREN’S LIBRARIANS SECTION OF THE AMERICAN LIBRARY ASSOCIATION
I keep the medal in the attic where I work.