Graffiti on a train car is not supposed to cover the reporting mark. If it does, the railroad is required to repaint the car. For this reason, artists are encouraged not to have their tags obscure the marks. This one is cool because the artist ENHANCED the marks instead of obscuring them. Kudos to you HBAK! CRDX is the reporting mark for Chicago Freight Car Leasing, the owner of the covered hopper in this image (the real one). Also Kudos the modeler who reproduced HBAK's work on a scale model train.