ALL cars were special ordered, but not in the way you might think. Chevrolet didn't build cars and then just ship them helter skelter hoping they would sell. Cars were ordered by dealers. Some for "stock" (the ones you found on the lot when you went "window shopping"), and some (special ordered) by customers. Your car was ordered by Gibson Chevrolet for "stock" and delivered to Gibson Chevrolet once the car was built.
John once went over the ordering process but I can't seem to find it. Maybe he'll chime in again, but in a nutshell, the dealer filled out the order form for what he wanted and sent it to the local Zone Office. If there weren't any issues, the Zone Office forwarded it to the Central Office in Detroit. If THEY didn't find any issues, the Central Office forwarded it to the local factory (Norwood or LA) for the car to be scheduled and built. If there WERE issues (for example, an option that wasn't available, an axle ratio that wasn't on the Power Team chart, etc...), the order was kicked back to the dealer to resolve. Once the car was built, it was shipped to the ordering dealer for "inventory" or to be delivered to the customer that "special ordered" it.