HA...! That just caused me to do some reading...
First of all, I was wrong. The framed car door is hard to see in your first picture. I mistook it for what I refer to as the bubble top, while the second picture is obviously a car door model.
I think it is interesting that so many modification were done by Hawker to this airplane and it remained the IB.
I wrongly though that the car door was the IA while the bubble top was the IB but the literature only refer to them as early and late.
I did find however find a comment that was worthy of notice. That was that it was not unusual for the car door to come open in flight. Therefore the left hand door was sealed . This also explains why I never saw a picture of left door opened.
Thanks Pauls . Cheers, Christian B)