CNW began painting F-units in the simplified yellow/green with “Chicago and North Western” spelled out on the fl anks and nose shields by 1961. The engines retained their four digit 4000 series numbers until 1971-72 when the remaining F-units that hadn’t been traded in on newer units were numbered into the 200 series for A units and the 300 series for B units with CNW heralds on the nose and sides in simplified yellow/green. Units painted in the original black/yellow/green scheme could be found still in the late 60s.