This model dates to the early days of N scale (late 60's / early 70's). It was originally imported by Aurora/Minitrix (and later on by Model Power). Roco made a similar (but not exactly the same) gondola for AHM (and later on, Con-Cor). Model Power dropped this model from their catalog circa 1980.
I'm told that this particular model is a good match for the PRR/PC G36c gondola built in the early 1960s. For the most part, gondolas such as these are actually 52' or 53' 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.