George III 1788 gold Pattern Sixpence, by J. P. Droz, extremely rare

George III (1760-1820), Pattern Sixpence, 1788, struck in gold, by Jean-Pierre Droz, crowned GR cypher within laurel wreath, toothed outer border surrounding, rev. struck en medaille, Britannia seated left on globe, holding spear and olive branch, heraldic shield behind, date in exergue, legend BRITAN NIA. with beaded outer border surrounding, edge straight grained, weight 3.55g (Bole 1740 this coin; WR 151, ESC 1643 R6; Bull 2217 R5; S.-). With one light crease across coin, reddish tone with good residual detail, graded by NGC as XF Details, extremely rare, one of only three examples in commerce.