When passenger trains were the predominant form of cross-country travel, most every train had one or more railway post office (RPO) cars. These cars were essentially mobile post offices, picking up, sorting, and delivering the mail all along the train's route. Recently, MTH has brought out a newly tooled version of the RPO which is a pretty neat model. I've done a review of two of the versions, one for the PRR and one for the CNJ Blue Comet. The review, with photos, is on the Train Reviews page of my web site . Here are the overview shots of both cars.