The Southern San Luis Valley RR was only about 1.5 miles (2.4 km) long and ceased operations in 1996. This loco was built in the railroad's shops around 1955 and used until the end of service. It has been sitting out in the open since then. A chain drive was used to propel it, which you can see between the trucks. Here is a link to a web page that describes the mechanics of the vehicle with pictures of the interior:
https://vintagedieseldesign.com/2020/09/14/a-home-built-locomot..-500/