This  is 2.5 by 2 inches. The Chicago, Rock Island & Pacific Rail Road went from Chicago to Denver in the west and Texas in the south. Pacific?  The railroad started in 1852  and ended in 1980.  It mostly went south and a bit west of Chicago.

 This new version of the old badge has no pin as can be seen on the back. It weighs about .75 ounce.   

THE BADGE LOOKS GOLD IN THE PHOTO, BUT THAT IS JUST THE PHOTO -  IT IS STERLING SILVER.  I have not polished it at all, but it should clean up nicely.