This grisaille on a brown ground enamel decoration enjoyed great popularity in late 18th century London and is associated with enamellists such as James Morisset, Louis and Simon Augustin Toussaint, William Charron and, probably, Gabriel Wirgman.
For a similar type of decoration, see lot 7 in Works of Art from the Collection of S.A.R. La Principessa Reale Maria Gabriella Di Savoia, Christie's, London, 27 june 2007 and lot 820 in The Dr Anton C.R.Dreesmann Collection Gold Boxes, Objects ofVertu and Portrait Miniatures, Christie's, London, 11 April 2002.