The Nederlandse Spoorwegen (NS) Class 200 diesel locomotives were built for shunting duties. 169 of these small locomotives, numbered 201-369, were built by Werkspoor from 1934–1951. They were known as "Sikken" (Sik in singular, goats because of their whistle sounding like a bloating goat) by rail enthusiasts and "locomotor" by railway staff. Fifteen of these locomotives were rebuilt with a retractable crane. Many are preserved; regular service has stopped a few years ago.

The design and operation was based on the simplest of things, which in effect made them very reliable. The locomotive was operated by design from the outside (side of engine) and wasn't equipped with a dead man device to stop the locomotive automatically in case of incapacity of the operator. There were two manual brakes: a handle and a foot brake. As the handle could be moved by in-train forces while dead-heading it was required to be fixed by a nut and bolt. Upon taking the locomotive into service again, it was necessary to loosen the nut and bolt. In some cases this was forgotten and the result was that the operator couldn't brake; many Siks have suffered collision damage due to this.

A special design was implemented for coolant; the fuel tank with diesel was also the coolant for the engine. The theory was that the coolant would never be exhausted while the locomotive is in use.

The locomotive didn't have an air pressure system. To obtain a whistle a device was put on top of the exhaust to use the flow of exhaust gases as the whistle air. This resulted in a very characteristic whistle sound (to imitate the sound, whistle a high-pitched tone while making a rolling R sound).

This locomotive was mainly operated as a shunter. Only a very few fully qualified train engineers/drivers have held a locomotor license.