This model (Roco's so-called "jumbo hopper") dates back to the early days of N scale (late 60's / early 70's). It has had various importers over the years (AHM first, Con-Cor later on). Despite the "52 foot" designation, I'm told that the model actually scales out considerably longer than that (more like 60').
Although not a particularly close match to any actual prototype, the general consensus seems to be that it's a kinda / sorta decent representation (IE, "foobie") of a Southern "Big John" grain hopper (built around 1962). As of this writing (2009), the Big Johns that still remain in service are definitely reaching their "mandatory retirement" age.