Oval, on ivory, in a rectangular carved gilt-wood frame, 9cm.
The reverse is inscribed: ‘copy’d at Rome in 1769 by Mme Maron Sister to Mr Mengs, principal painter in Spain, from Guido’s Sybil in Mr. Wilbraham’s collection’.
Theresia Mengs was born to German parents in Usti nad Labem in Bohemia. She and her brother, the artist Anton Raphael Mengs (1728-1779), were pupils of their father Ismael, who was court painter to the Elector of Saxony.
She worked for a short time at the court in Dresden before moving to Rome, where she became a successful painter of portraits and miniatures in pastel, gouache and enamel.
She married the Austrian artist Anton von Maron (1733-1808), in 1765.