Caption on reverse: "BS6..credit INP SOUNDPHOTO..4/9/51..Boston...Reports from Cannes, France, today reveal that Boston and North Shore socialite Nancy Clark Bertelsen Masseroni is the constant companion of Prince Aly Khan. The Hub beauty, who has taken flings at singing, acting, modeling and flying was pictured above when singing at a Boston hotel. The Prince's wife, Rita Hayworth, …