What year did the full length dome cars show up on railroads? 1955?
Early 50's I think.
I think that the first full length dome was used on the Milwaukee Road 'Olympian Hiawatha' luxury train of 1952.
By coincidence I was looking at a Youtube video of it only last week. It's a great film. See http://www.youtube.com/watch?v=RevpfzJPqiQ