King Frederick William I, son of King Frederick I of Prussia (1657-1713) and his wife, Sophia Charlotte (1668-1705, see lot 64) laid the foundation of power for the success of his son, Frederick the Great (see lot 63). Known as the 'Soldier King', he was a passionate soldier and notorious for his personal regiment of very tall soldiers, Lange Kerls. He also excelled at administration and established a central hierarchy of adminstrative offices that gave Prussia the most advanced bureaucracy in Europe.
Johann Harper worked in Berlin from 1712 and was styled Hof-Kabinettmaler to King Frederick William I from 1716. For further information on Harper, see Boo von Malmberg, 'Johann Harper', Konsthistorisk Tidskrift, XXIII, nos. 3-4, Stockholm, 1954/55, pp. 86-89.
An enamel miniature of the same sitter by Harper, signed and dated 1733 with address Berlin, was sold Christie's, Geneva, 14 May 1991, lot 136.
A slightly smaller variant of the present enamel depicting the king without the breast-star, was illustrated in the exhibition catalogue Kaiserlicher Kunstbesitz aus dem holländischen Exil Haus Doorn, Berlin, Charlottenburg Castle, 1991, p. 30, no. 9.3. Helmut Börsch-Supan's catalogue notice specifies that the miniature is based on Antoine Pesne's full-length portrait of 1729, now at Charlottenburg Castle, and that the author of the enamel could be Johann Harper.