The Rocket Box Wagon is a steam-era open wagon with a longer-than-average wheelbase, carrying a load of barrels. Open wagons like this would have been used on the Liverpool & Manchester Railway (the company who held the contest to which Rocket was one entry) but usually for moving textiles instead. This wagon probably also dates much later than the original rocket. It has no buffers much like the tender wagon and the rocket, though in reality this later model would have had them.
This wagon has a good cargo size but a low maximum speed. It is the only one from the Rocket set that has no crafting recipe.