Dear Adrienne,
I don't know, but if I wanted to find out, I'd ask Andrew Butterfield, at
Christie's, who was a student of Sir John's at the NYU Institute of Fine
Arts (that institution may well be able to tell you something, too).
good luck,
Peter Chametzky

Associate Professor of Art History
School of Art and Design
Southern Illinois University
Carbondale, IL 62901

(618) 453-8632