Thanks for the info. It is correct that this model was brought over to Europe, but according to someone, these flat cars came orgianlly from North America - aorund WWII time. Oh well, too bad. The legnth on the photo indicated a proportion of a 40' car, as far as I know there are no 40" low sided gondolas on the RhB, they are all shorter and 2 axle only.
I will keep on searching.
I will keep on searching.