Details & Changes.

The ventilation window until ch.number 20-041711. Note the difference in the handle for the sliding
window catch. This type were on all barndoors.

Except from small changes the ventilation window look like this from ch.number 20-041712 until end of splitt screen window buses in 1967.

Handle for ventilation window on front door until ch.number 20-041711 (left)
Handle for ventilation window on front door from ch.number 20-041712.