The SS 1600 class, later redesignated as the CC50 class, is a 2-6-6-0 articulated Mallet type steam locomotive previously operated by the Staatsspoorwegen (SS), which was built by Werkspoor and the Swiss Locomotive and Machine Works (SLM).

The Staatsspoorwegen (SS) ordered 30 1600 class Mallets from several European firms such as Werkspoor and the Swiss Locomotive and Machine Works (SLM) between 1927-1928.

The 1600s distinguished themselves by pulling a train weighing 1,300 tons at a speed of 55 km/h (34 mph), and also with their good cornering abilities.

In 1981, number 22 of Purwokerto was donated by PJKA to the Utrecht Railway Museum, as a symbol of friendship between Indonesia and the Netherlands.

Apart from that, number 19 of Purwakarta became the main star in the War of Independence themed film entitled The Last Train in the same year.