Nicholas Turner, in a letter of 6 June 1984, dated this drawing to the late 1630s or early 1640s. Sir Denis Mahon has also, on the basis of a photograph, kindly confirmed the attribution to Guercino.
A drawing of the same subject is in the Pierpont Morgan Library, New York, D.M. Stone, Guercino, Master Draftsman, works from North American Collections, exhib. cat., Arthur M. Sackler Museum, Cambridge and elswhere, 1991, checklist no. 134, pl. M.