Fatman, based on what I've seen it looks like Hafner changed the colors of the litho brick and stone sides, roof enamel color, and perhaps even base colors (I say perhaps because I have seen some green bases but I couldn't decide if they were original or repaints). However, I haven't seen anything that would suggest a timeline for these changes.
To your station - I have one like it too - less the semaphore. It is obvious from the wear marks on the extreme right hand side of the station that it did have a semaphore at one time but it was long gone by the time I found it.
