Seal of the Stewards
The Seal of the Stewards' was the seal of the Stewards of Gondor, consisting of the letters R·ND1·R below three stars. The letters represent the word Arandur. This is the actual Elvish title, literally meaning 'King's Servant', that Tolkien renders into English as 'Steward'.
When the twelfth Steward, Cirion, sent north to Eorl for aid in his desperate wars, he sent the Seal with each of six riders. Only one of these, named Borondir, succeeded in reaching the nation of the Éothéod, but from this came the famous Ride of Eorl and the foundation of Rohan.