Knob for starting a Mercedes-Benz 220 D (W123)

To start an early diesel Merc you had to:
- put the key into the ignition in position II
- pull this knob to pre glow the engine
- pull this knob further after preglowing to engage the starter motor

Once the engine had started you let go of this knob. In this picture the knob is in the driving position (engine on).

By turning the knob you could control the engine idle speed (for cold engines).

The Mercedes-Benz W123 was the last Mercedes to have a knob for starting.