John Wesley was influenced by the deep faith and spirituality of the Moravian brotherhood, a religious group from Germany. The brotherhood was led by Nikolaus Ludwig, Reichsgraf ('Count') von Zinzendorff und Pottendorf (1700 – 1760), a German religious and social reformer, who became bishop of the Moravian Church. Wesley travelled to Germany and met the Count twice, and the famous meeting where Wesley experienced his conversion experience in London in 1738 had Moravian links.
This Moravian seal impression is mounted on a piece of cardboard inscribed: "The seal of the United Brethren/The Moravian or United Brethrens (sic) Seal/Given to me 1739./ John Wesley".
See also the Moravian bible and the portrait of Count Zinzendorff in the Online Collection.