This uniface medal bears Samuel Longhorn Clemens (a.k.a. Mark Twain) seated in an easy chair holding a calabash pipe, facing left. In upper left, MARK TWAIN / CENTENARY OF HIS BIRTH / MDCCCXXXV-MCMXXXV. Below, between two standing figures of Huck Finn and Tom Sawyer, ALWAYS DO RIGHT / THIS WILL GRATIFY / SOME PEOPLE / AND ASTONISH THE / REST.
For a long time this plaque was not recognized as a member of the prestigious Society of Medalists series. It was designed and is dated 1935 but it was actually first released to the wider public in 1950 as the first special commemorative issue of the series to celebrate the Society's 20th anniversary.
As it predates the series and was only re-released under the Society's imprimatur one can debate its status as a SOM medal, but regardless, it is a beautiful medal that deserves a place in your Society of Medalists collection.
References: MACo 1935-015, Marqusee 148