All the original intermediates for the 80 class had the middle doors,however,when the GMs took over the NIR Enterprise duties in1981 with a new batch of coaches,some of the original Enterprise coaches that ran behind the Hunslet's were converted to 80 class intermediates and these did not have the centre doors.The shots of the 2 class 80 intermediate coaches that you posted in your earlier post,while being well painted,are wrong as they only have 7 windows which were what the old first class coach had and these were not converted to run with the 80 class.The standard opens with 8 windows were the only type converted,a Lima SO second class coach can be picked up quite cheap and re painted to give an authentic intermediate coach from the early 80s onwards.