According to a book I have, now out of print-" Moving Mail and Express by Rail ", the very last day of the RPO's was in September and October of 1967. Of note..The RPO did not operate in Canada.
Thankyou all for your response...that would explain the 'baggage-like' doors on the car. My next question is, does anyone know when CN railway dropped these cars from passenger service? '60's? 70's? ???