Capt:
I have almost the exact same set, and Eric is right, door is missing! However I have another Admiral which has a door that measures the same size and has the same mount, but is the reversed painted plastic because the set is like that. Also it is a vertical door but I bet you could extrapolate a close approximation to the original from it. My set that is missing the door is just brown plastic for the adjacent components. Hope this helps!
Marlin