A pair of adapter coupler cars. The Railway Express 478 boxcar has a knuckle coupler at one end and an American Flyer 3/16" O gauge link coupler at the other.
The 2655 Railway Express boxcar (numbered 6572-75) has a postwar truck at one end and a box coupler compatible with 600/2600 series cars at the other.
Middle photo is a train with the adapter coupler car.