I made the building about 20 years ago. It is as closely based on the Swifty Meat Processing plant of the 1949 Lionel Showroom layout as possible. Frank Ellison is the original designer and there are plans with measurements in the Model Railroading books put out by Lionel via Bantam. From the 6th edition, for example, on pages 214-15 are measurements and discussion (it is called a Small Parts Factory there).
The roof was intended to replicate the roof on the Lionel Showroom layout version. I used heavy construction paper for the material, then randomly sprayed a little paint to make it uneven.
The basic structure is alot of 1/8" plywood. The windows and doors are from Lionel, places like 445 switch tower. You could buy alot of them for really cheap; perhaps still can. Too white - need weathering.
The platform is scratch built with basswood. Should be stained/aged. Looks too new.
The building has a foundation made of plaster with rocks added in. Looks perhaps like 19th century New England foundations.
The oil tank probably came from Berkshire. They have tons of great detail items.
If any of these areas need expansion, I would be happy to provide them.