Railroads provided their own security and identification to secure their own property and to be sure that people riding the trains had paid their fares. Badges from railroads are collected by badge collectors and railroad collectors alike. Railroads operated starting in the mid to late 1800s and badges from the earliest steam engine periods will be the most valuable.
Below are some examples of railroad badges, you can tell what railroad it is for by the abbreviations (B&O is Baltimore and Ohio for example). For more information visit my other site on railroads at http://railroadcollectibles.com.