Train cars needed lighting fixtures, sinks, toilets, shelfs, luggage racks, and other types of fixtures just like anything else and some of these objects have managed to be preserved over time. While most railroad car parts were scrapped, reused, or destroyed when a car was taken out of service some pieces have managed to make it into collections. The most common items to see are lighting sconces or chandeliers, windows, sinks, toilets, door handles, and other architectural type features. Probably the most collectible of these types of items will be from Pullman railway cars. Pullman had a monopoly on the manufacture of passenger cars, luxury sleepers, business cars, and other coaches for wealthy individuals so most of the nice collectible objects will be from Pullman.
Condition, rarity, railroad, and age all play key roles in determining value, but things that people can reuse, or incorporate into their collections obviously have the most value.