Tony, note that 20000-20048 were AAR BX express box and 20050-22414 (1175 cars in my 1-1-50 ORER) were AAR XM. In both groups CMO used even numbers only. Also note that the express versions were built with Allied full cushion trucks and later got regular passenger trucks.  The in-service photo of 20024 was taken in Waukesha WI in 1970 long after CNW/CMO passenger service had been reduced to Chicago area commuter trains except for a hold out from Chicago to Green Bay that disappeared with the coming of Amtrak.  Hope this helps. Tony Wagner