By 1956, most railroads had nearly completed the replacement of steam with Diesel, so the steam locomotive in yesterday’s booklet has been replaced with three Diesels. It looks like someone took an Xacto knive and removed the steamer, leaving a white background, which may explain why the entire freight train has a white background–it replaced some other train from an earlier edition. For this edition, they also gratuitously replaced the EMD-looking Diesels on the passenger train with ones looking more shark-nosed.
Inside, the contents of the two booklets are similar, but some of the photos have been updated or changed. The inside front cover photo of a bridge under construction, for example, has been replaced by one of the vista-dome North Coast Limited going over a bridge near Butte, Montana.