191.078.013 is a part manufactured by Marquardt, a German company that produces electrical, pneumatic, and other components. This part specifically is an "On-off switch with locking lever," designed to provide an easy-to-use mechanism for switching electrical circuits on and off. This part would typically be used in medium- to heavy-duty electrical applications, such as motor drives, pumps, and circuit breakers. The locking lever helps to ensure that the switch remains in the desired position, and can be used as an additional safety measure.