This is a 10,000 gallon, single-dome tank car. The "X" in the road name's "SHPX" stands for a private company-owned car, rather than a railroad-owned car. The Shippers Car Line company owned the car and leased it to another company for use. During the lease, the other company's name and information would be stenciled on the car. The prototype photo below is the best I could find. There were lots of these cars out there, but probably few people bothered to photograph them. There are lots of photos of Shippers Car Line tank cars in the "American Car & Foundry Company 1899-1999" book, but none that seemed to match the model. (photo source: Tomlin Ordnance Depot; web site is now gone). Fellow S-scale modeler, Earl Tuscon found the prototype that matches the model to be the ACF Type 27 car, with the range of road numbers being #10762 through #10811. These were built in June, 1930 (see RPC Vol. 3).