Sarah ('Sally') Gwynne (1726-1822) married Charles Wesley in 1749. The marriage was happy and produced two sons, both well-known musicians.
The engraving shows Mrs Wesley at the age of ninety eight, living in London, shortly before her death that same year. The image is signed 'Blood ft'; probably, it was engraved by Thomas Blood (1777-1850), a well-known British engraver of the early 1800s. Compare also with the small oil sketch of Sarah Wesley in the Online Collection, 1997/6629.