I ran across the original of this engraving a couple days ago & recalled it was done when he was a youngster.
I did a bit of searching just now & came up with the following about the original painting:

Prince Charles Edward Stuart
studio of Antonio David
oil on canvas, feigned oval, circa 1729-1732
25 in. x 19 in. (635 mm x 483 mm)
Purchased, 1876
On display Beningbrough Hall, on Floor 1: Lady Chesterfield's Dressing Room at Beningbrough Hall

http://www.npg.org.uk/live/search/po...rNo=0&role=sit