Yep, a quick Google search reveals that C57 is the class of locomotive, of which No. 180 is preserved and in working order, and No. 135 is on static display in a museum.
And after snooping around Ripley's profile nonchalantly cuz he happened to be online and reading an old post he was reading, it seems that there are minor differences and modifications made between members of the class... Most notably being the colors of the valve gear, shapes of the smoke deflectors, and in some cases their funnels or cab-backs.
All the credit goes to ripley802, as I'm fairly certain he was about to say the same thing