This car dates back to the early days of N scale (late 60's / early 70's). It was originally imported by AHM (and by Con-Cor later on). Roco made a similar (but not exactly the same) covered gondola for Minitrix/Model Power.
I don't know what specific prototype this model might have been based on (if any), but it's at least reminescent of a Pullman-Standard PS-5 (produced between 1949 and 1970). Gondolas such as these were generally 52' in real life (as opposed to 50'). The reason N scale has so many 50' gondolas is simply because it allowed manufacturers to save money by recycling the 50' underframes from their box cars.
Covered gondolas like these were commonly used for transporting steel coils and rolled bar stock - loads that needed protection from the elements, yet weren't easily placed inside of box cars. The triangular "points" on the cover (see above picture) are lift hook points. The covers generally lift off in two or three separate sections.