According to the 1973 catalogue the inscription is perhaps by a Neapolitan hand.
Dr Miriam di Penta has kindly confirmed the attribution. The drawing will be included in her forthcoming catalogue raisonné of the artist.
Signature: With inscription 'Gio Beo Castiglione'
Marchese del Carpio.
Anonymous sale; Christie's, London, 20 March 1973, lot 9 (as G.B. Castiglione; 180 gns to A. Stein).
With Charles E. Slatkin Galleries, New York (as Castiglione).