The following text from Aviation Week is not unique to the aircraft pictured:
02/03/1964. Aero Spacelines, Inc., has obtained options to purchase two English-built Saunders-Roe Princess Flying boats from the still-unidentified European company which recently bought the three existing Princesses from the British govenment. Aero Spacelines plans to submit an unsolicited proposal to NASA to convert the flying boats into turbofan, land-based aircraft to haul Saturn rocket stages. View also photo 44 and 10571.