PURPOSE: To facilitate judgement on an operational condition.

CONSTITUTION: A projected section 15b projected out of a hole 7a provided for a arc distinguishing cover 7 at its restoring position is provided at a part of a movable contact shoe base 15. The tip end section 15c of the projected section 15b is so constituted as to be roughly identical in diameter to the hole 7a of the arc distinguishing cover 7, and the root section 15d of the projected section 15b is made slenderer than the tip end section 15c. The side face of the projected section 15b or the circumference of the root section 15d or both of them are coated with paint different in color from its circumference.