A circuit breaker includes a housing; separable contacts; an operating mechanism having a movable operator handle with an OFF position and an ON position; and a handle lock device. The handle lock device includes: a member secured to the housing, a flange on the member disposed alongside the operator handle, an opening in the flange adapted to receive only one shackle and having a perimeter which includes first opposing portions adapted to receive a cross section of a safety lockout shackle and to restrain rotation of the shackle within the opening. The shackle blocks movement of the operator handle from the OFF to the ON position thereof. The perimeter also includes second opposing portions adapted to alternatively receive the different cross section of a shackle of a padlock with that shackle blocking movement of the operator handle from the OFF to the ON position thereof.