In South and West Sumatra, like Java, the classification follows the Japanese system whereby a letter denotes the number of driving axles with a number to indicate the class, tank locomotives starting at 10 and tender locomotives at 50. The North Sumatra system was the former privately owned Deli Railway and the original numbers were kept.

In each case I have included some notes about the origins of the locomotives.

The current location of preserved examples is also given where known. There may be other locos preserved.