The Märklin 402 is one of the classic Märklin engines. It is of a convertible type and can be assembled into a vertical, an overtype or a lokomobile engine.

The box showing it as a power source for "Metallbaukasten", which was Märklin's Meccano-like construction set. The box dates this engine to around 1925-1929. Included is an inspectors' ticket showing it has passed the quality control, and some tools and accessories for maintaining the engine. The conical container in front contains oil.

The most common way of assembling this model would be as a lokomobile. The mechanics of this engine is quite complex and of high quality.