That is a good question Robert. It is a generic freight station and made by several manufacturers, Bing and Kraus are the most near the answer I think. They are not uncommon pieces and there is several color variations. The bing one is supposed to have an opening door on it's side.
Here is a similar one I have, no mark anywhere also and more simple than yours. I have thought Bing during a long time but would also be happy to learn more. Maybe our friend from Germany, Arne will have the correct answer.
Daniel