This item is a set that is in excellent condition, never used or displayed, no defects whatsoever.  Stored for many years. Features on #6-52099 are Die-Caast Trucks & Magnetic Couplers.  #6-52104 features Die-Cast Metal Cab, Detachable trailer w/die-cast metal chassis, opening rear doors, five axles and Opening tractor hood.  Beautiful addition to someone's Lionel collection.