Claycrossjunction

Hello.

My layout era is the late 1960s I thinking of buying an Bachmann Royal Mail coach . The one thing I have noticed on the Bachmann models is the door design on some models you have an half glass design on the others a more robust design with a small glass panel near the top.

My question is when did they change the door design I am guessing the ' Great Train Robbery ' of 1963 would have seen some design changers. Were Royal Mail Coaches still painted red by 1969 or had been redone into the blue and grey scheme? I have had a go searching the net but found very little can anyone answer this question? 

Thank . Clay Cross Junction.