This model is based on a General American ICC-103 10,000 gallon tank car. I'm not sure when said car was actually built, but it looks a bit like cars used in the 30s and 40s. The wide dome (or manway) identifies it as a non-pressurized tank car. Cars such as these were used to transport oil, gasoline, corn syrup, etc.
In addition to being sold separately, these cars are also available in 4-unit "Runner Packs". George Hollwedel (Prototype N Scale Models) made a special run of these cars in Santa Fe TK-L paint.